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Liu G, Zuo DY, Yang P, He WJ, Yang Z, Zhang JB, Wu AB, Yi SY, Li HP, Huang T, Liao YC. A Novel Deoxynivalenol-Activated Wheat Arl6ip4 Gene Encodes an Antifungal Peptide with Deoxynivalenol Affinity and Protects Plants against Fusarium Pathogens and Mycotoxins. J Fungi (Basel) 2021; 7:jof7110941. [PMID: 34829228 PMCID: PMC8618893 DOI: 10.3390/jof7110941] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 10/31/2021] [Accepted: 11/03/2021] [Indexed: 12/12/2022] Open
Abstract
Deoxynivalenol (DON) is one of the most widespread trichothecene mycotoxins in contaminated cereal products. DON plays a vital role in the pathogenesis of Fusarium graminearum, but the molecular mechanisms of DON underlying Fusarium–wheat interactions are not yet well understood. In this study, a novel wheat ADP-ribosylation factor-like protein 6-interacting protein 4 gene, TaArl6ip4, was identified from DON-treated wheat suspension cells by suppression subtractive hybridization (SSH). The qRT-PCR result suggested that TaArl6ip4 expression is specifically activated by DON in both the Fusarium intermediate susceptible wheat cultivar Zhengmai9023 and the Fusarium resistant cultivar Sumai3. The transient expression results of the TaARL6IP4::GFP fusion protein indicate that TaArl6ip4 encodes a plasma membrane and nucleus-localized protein. Multiple sequence alignment using microscale thermophoresis showed that TaARL6IP4 comprises a conserved DON binding motif, 67HXXXG71, and exhibits DON affinity with a dissociation constant (KD) of 91 ± 2.6 µM. Moreover, TaARL6IP4 exhibited antifungal activity with IC50 values of 22 ± 1.5 µM and 25 ± 2.6 µM against Fusarium graminearum and Alternaria alternata, respectively. Furthermore, TaArl6ip4 interacted with the plasma membrane of Fusarium graminearum spores, resulting in membrane disruption and the leakage of cytoplasmic materials. The heterologous over-expression of TaArl6ip4 conferred greater DON tolerance and Fusarium resistance in Arabidopsis. Finally, we describe a novel DON-induced wheat gene, TaArl6ip4, exhibiting antifungal function and DON affinity that may play a key role in Fusarium–wheat interactions.
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Affiliation(s)
- Gang Liu
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan 430070, China; (G.L.); (D.-Y.Z.); (P.Y.); (W.-J.H.); (Z.Y.); (J.-B.Z.); (S.-Y.Y.); (H.-P.L.)
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Dong-Yun Zuo
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan 430070, China; (G.L.); (D.-Y.Z.); (P.Y.); (W.-J.H.); (Z.Y.); (J.-B.Z.); (S.-Y.Y.); (H.-P.L.)
- State Key Laboratory of Cotton Biology, Institute of Cotton Research of the Chinese Academy of Agricultural Sciences, Anyang 455000, China
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Peng Yang
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan 430070, China; (G.L.); (D.-Y.Z.); (P.Y.); (W.-J.H.); (Z.Y.); (J.-B.Z.); (S.-Y.Y.); (H.-P.L.)
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Wei-Jie He
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan 430070, China; (G.L.); (D.-Y.Z.); (P.Y.); (W.-J.H.); (Z.Y.); (J.-B.Z.); (S.-Y.Y.); (H.-P.L.)
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Zheng Yang
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan 430070, China; (G.L.); (D.-Y.Z.); (P.Y.); (W.-J.H.); (Z.Y.); (J.-B.Z.); (S.-Y.Y.); (H.-P.L.)
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Jing-Bo Zhang
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan 430070, China; (G.L.); (D.-Y.Z.); (P.Y.); (W.-J.H.); (Z.Y.); (J.-B.Z.); (S.-Y.Y.); (H.-P.L.)
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Ai-Bo Wu
- Key Laboratory of Food Safety Research Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China;
| | - Shu-Yuan Yi
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan 430070, China; (G.L.); (D.-Y.Z.); (P.Y.); (W.-J.H.); (Z.Y.); (J.-B.Z.); (S.-Y.Y.); (H.-P.L.)
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
- Forestry and Fruit Tree Research Institute, Wuhan Academy of Agricultural Sciences, Wuhan 430070, China
| | - He-Ping Li
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan 430070, China; (G.L.); (D.-Y.Z.); (P.Y.); (W.-J.H.); (Z.Y.); (J.-B.Z.); (S.-Y.Y.); (H.-P.L.)
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Tao Huang
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan 430070, China; (G.L.); (D.-Y.Z.); (P.Y.); (W.-J.H.); (Z.Y.); (J.-B.Z.); (S.-Y.Y.); (H.-P.L.)
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
- Correspondence: (T.H.); (Y.-C.L.)
| | - Yu-Cai Liao
- Molecular Biotechnology Laboratory of Triticeae Crops, Huazhong Agricultural University, Wuhan 430070, China; (G.L.); (D.-Y.Z.); (P.Y.); (W.-J.H.); (Z.Y.); (J.-B.Z.); (S.-Y.Y.); (H.-P.L.)
- College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
- Correspondence: (T.H.); (Y.-C.L.)
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Katsumata O, Mori M, Sawane Y, Niimura T, Ito A, Okamoto H, Fukaya M, Sakagami H. Cellular and subcellular localization of ADP-ribosylation factor 6 in mouse peripheral tissues. Histochem Cell Biol 2017; 148:577-596. [PMID: 28748255 DOI: 10.1007/s00418-017-1599-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/19/2017] [Indexed: 01/30/2023]
Abstract
ADP-ribosylation factor 6 (Arf6) is a small GTPase that regulates endosomal trafficking and actin cytoskeleton remodeling. In the present study, we comprehensively examined the cellular and subcellular localization of Arf6 in adult mouse peripheral tissues by immunofluorescence and immunoelectron microscopy using the heat-induced antigen retrieval method with Tris-EDTA buffer (pH 9.0). Marked immunolabeling of Arf6 was observed particularly in epithelial cells of several tissues including the esophagus, stomach, small and large intestines, trachea, kidney, epididymis, oviduct, and uterus. In most epithelial cells of simple or pseudostratified epithelia, Arf6 exhibited predominant localization to the basolateral membrane and a subpopulation of endosomes. At an electron microscopic level, Arf6 was localized along the basolateral membrane, with dense accumulation at interdigitating processes and infoldings. Arf6 was present in a ring-like appearance at intercellular bridges in spermatogonia and spermatocytes in the testis and at the Flemming body of cytokinetic somatic cells in the ovarian follicle, thymus, and spleen. The present study provides anatomical clues to help understand the physiological roles of Arf6 at the whole animal level.
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Affiliation(s)
- Osamu Katsumata
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa, 252-0374, Japan
| | - Momoko Mori
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa, 252-0374, Japan
| | - Yusuke Sawane
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa, 252-0374, Japan
| | - Tomoko Niimura
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa, 252-0374, Japan
| | - Akiko Ito
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa, 252-0374, Japan.,Department of Anesthesiology, Kitasato University School of Medicine, Sagamihara, Kanagawa, 252-0374, Japan
| | - Hirotsugu Okamoto
- Department of Anesthesiology, Kitasato University School of Medicine, Sagamihara, Kanagawa, 252-0374, Japan
| | - Masahiro Fukaya
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa, 252-0374, Japan
| | - Hiroyuki Sakagami
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa, 252-0374, Japan.
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Integrin-Dependent Regulation of Small GTPases: Role in Cell Migration. J Indian Inst Sci 2017. [DOI: 10.1007/s41745-016-0010-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Shigella flexneri regulation of ARF6 activation during bacterial entry via an IpgD-mediated positive feedback loop. mBio 2015; 6:e02584. [PMID: 25736891 PMCID: PMC4358011 DOI: 10.1128/mbio.02584-14] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
UNLABELLED Entry into cells is critical for virulence of the human bacterial pathogens Shigella spp. Shigella spp. induce membrane ruffle formation and macropinocytic uptake, but the events instigating this process are incompletely understood. The host small GTPase ADP-ribosylation factor 6 (ARF6) functions in membrane trafficking at the plasma membrane and activates membrane ruffle formation. We demonstrate that ARF6 is required for efficient Shigella flexneri entry, is activated by S. flexneri dependent on the phosphatase activity of the type III secreted effector IpgD, and depends on cytohesin guanine nucleotide exchange factors (GEFs) for recruitment to entry sites. The cytohesin GEF ARF nucleotide binding site opener (ARNO) is recruited to these sites, also dependent on IpgD phosphatase activity. ARNO recruitment is independent of ARF6, indicating that, in addition to the described recruitment of ARNO by ARF6, ARNO is recruited upstream of ARF6. Our data provide evidence that ARF6, IpgD, phosphoinositide species, and ARNO constitute a previously undescribed positive feedback loop that amplifies ARF6 activation at bacterial entry sites, thereby promoting efficient S. flexneri uptake. IMPORTANCE Shigella spp. cause diarrhea and dysentery by infection of epithelial cells in the human colon. Critical to disease is the ability of Shigella to enter into cells, yet the mechanisms involved in entry are incompletely understood. We demonstrate that the small GTPase ADP-ribosylation factor 6 (ARF6) is required for efficient cellular entry of Shigella flexneri and that activation of ARF6 depends on the phosphatase activity of the Shigella protein IpgD, which is introduced into cells via the bacterial type III secretion system. We further show that IpgD phosphatase activity is required for recruitment of the ARF6 guanine nucleotide exchange factor (GEF) ARF nucleotide binding site opener (ARNO) to bacterial entry sites and that ARNO lies upstream of ARF6 activation. These relationships define a positive feedback loop that contributes to activation of ARF6 at S. flexneri entry sites and leads to local amplification of signals that promote bacterial entry.
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Grp1-associated scaffold protein (GRASP) is a regulator of the ADP ribosylation factor 6 (Arf6)-dependent membrane trafficking pathway. Cell Biol Int 2013; 36:1115-28. [PMID: 22931251 DOI: 10.1042/cbi20120221] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
GRASP interacts with Grp1 (general receptor for phosphoinositides 1; cytohesin 3), which catalyses nucleotide exchange on and activation of Arf6 (ADP-ribosylation factor-6). Arf6 is a low-molecular-mass GTPase that regulates key aspects of endocytic recycling pathways. Overexpressed GRASP accumulated in the juxtanuclear ERC (endocytic recycling compartment). GRASP co-localized with a constitutively inactive mutant of Arf6 in the ERC such that it was reversed by expression of wild-type Grp1. Co-expression of GRASP and Grp1 promoted membrane ruffling, a cellular hallmark of Arf6 activation. GRASP accumulation in ERC was found to block recycling of the MHC-I (major histocompatibility complex-I), which is trafficked by the Arf6-dependent pathway. In contrast, overexpression of GRASP had no effect on the recycling of transferrin receptors, which are trafficked by a clathrin-dependent pathway. The findings suggest that GRASP regulates the non-clathrin/Arf6-dependent, plasma membrane recycling and signalling pathways.
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Abstract
We have previously reported the development of small molecule phosphatidylinositol-3,4,5-trisphosphate (PIP3) antagonists (PITs) that block pleckstrin homology (PH) domain interaction, including activation of Akt, and show anti-tumor potential. Here we show that the same molecules inhibit growth factor-induced actin remodeling, lamellipodia formation and, ultimately, cell migration and invasion, consistent with an important role of PIP3 in these processes. In vivo, a PIT-1 analog displays significant inhibition on tumor angiogenesis and metastasis. ADP ribosylation factor 6 (ARF6) was recently identified as an important mediator of cytoskeleton and cell motility, which is regulated by PIP3-dependent membrane translocation of the guanine nucleotide exchange factors (GEFs) such as ADP-ribosylation factor nucleotide binding-site opener (ARNO) and general receptor for 3-phosphoinositides (GRP1). We demonstrate that PITs inhibit PIP3/ARNO or GRP1 PH domain binding and membrane localization, resulting in the inhibition of ARF6 activation. Importantly, we show that expression of the constitutively active mutant of Arf6 attenuates inhibition of lamellipodia formation and cell migration by PITs, confirming that inhibition of Arf6 contributes to inhibition of these processes by PITs. Overall, our studies demonstrate the feasibility of developing specific small molecule targeting PIP3 binding by PH domains as potential anti-cancer agents that can simultaneously interfere with cancer development at multiple points.
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Akiyama M, Zhou M, Sugimoto R, Hongu T, Furuya M, Funakoshi Y, Kato M, Hasegawa H, Kanaho Y. Tissue- and development-dependent expression of the small GTPase Arf6 in mice. Dev Dyn 2010; 239:3416-35. [DOI: 10.1002/dvdy.22481] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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Impact of female cigarette smoking on circulating B cells in vivo: the suppressed ICOSLG, TCF3, and VCAM1 gene functional network may inhibit normal cell function. Immunogenetics 2010; 62:237-51. [PMID: 20217071 DOI: 10.1007/s00251-010-0431-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Accepted: 02/03/2010] [Indexed: 12/11/2022]
Abstract
As pivotal immune guardians, B cells were found to be directly associated with the onset and development of many smoking-induced diseases. However, the in vivo molecular response of B cells underlying the female cigarette smoking remains unknown. Using the genome-wide Affymetrix HG-133A GeneChip microarray, we firstly compared the gene expression profiles of peripheral circulating B cells between 39 smoking and 40 non-smoking healthy US white women. A total of 125 differential expressed genes were identified in our study, and 75.2% of them were down-regulated in smokers. We further obtained genotypes of 702 single nucleotide polymorphisms in those promising genes and assessed their associations with smoking status. Using a novel multicriteria evaluation model integrating information from microarray and the association studies, several genes were further revealed to play important roles in the response of smoking, including ICOSLG (CD275, inducible T-cell co-stimulator ligand), TCF3 (E2A immunoglobulin enhancer binding factors E12/E47), VCAM1 (CD106, vascular cell adhesion molecule 1), CCR1 (CD191, chemokine C-C motif receptor 1) and IL13 (interleukin 13). The differential expression of ICOSLG (p = 0.0130) and TCF3 (p = 0.0125) genes between the two groups were confirmed by real-time reverse transcription PCR experiment. Our findings support the functional importance of the identified genes in response to the smoking stimulus. This is the first in vivo genome-wide expression study on B cells at today's context of high prevalence rate of smoking for women. Our results highlight the potential usage of integrated analyses for unveiling the novel pathogenesis mechanism and emphasized the significance of B cells in the etiology of smoking-induced disease.
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Anthonio EA, Brees C, Baumgart-Vogt E, Hongu T, Huybrechts SJ, Van Dijck P, Mannaerts GP, Kanaho Y, Van Veldhoven PP, Fransen M. Small G proteins in peroxisome biogenesis: the potential involvement of ADP-ribosylation factor 6. BMC Cell Biol 2009; 10:58. [PMID: 19686593 PMCID: PMC3224584 DOI: 10.1186/1471-2121-10-58] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Accepted: 08/17/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Peroxisomes execute diverse and vital functions in virtually every eukaryote. New peroxisomes form by budding from pre-existing organelles or de novo by vesiculation of the ER. It has been suggested that ADP-ribosylation factors and COPI coatomer complexes are involved in these processes. RESULTS Here we show that all viable Saccharomyces cerevisiae strains deficient in one of the small GTPases which have an important role in the regulation of vesicular transport contain functional peroxisomes, and that the number of these organelles in oleate-grown cells is significantly upregulated in the arf1 and arf3 null strains compared to the wild-type strain. In addition, we provide evidence that a portion of endogenous Arf6, the mammalian orthologue of yeast Arf3, is associated with the cytoplasmic face of rat liver peroxisomes. Despite this, ablation of Arf6 did neither influence the regulation of peroxisome abundance nor affect the localization of peroxisomal proteins in cultured fetal hepatocytes. However, co-overexpression of wild-type, GTP hydrolysis-defective or (dominant-negative) GTP binding-defective forms of Arf1 and Arf6 caused mislocalization of newly-synthesized peroxisomal proteins and resulted in an alteration of peroxisome morphology. CONCLUSION These observations suggest that Arf6 is a key player in mammalian peroxisome biogenesis. In addition, they also lend strong support to and extend the concept that specific Arf isoform pairs may act in tandem to regulate exclusive trafficking pathways.
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Affiliation(s)
- Erin A Anthonio
- Department of Molecular Cell Biology, Catholic University of Leuven, Leuven, Belgium.
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Sironi C, Teesalu T, Muggia A, Fontana G, Marino F, Savaresi S, Talarico D. EFA6A encodes two isoforms with distinct biological activities in neuronal cells. J Cell Sci 2009; 122:2108-18. [DOI: 10.1242/jcs.042325] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The processes of neurite extension and remodeling require a close coordination between the cytoskeleton and the cell membranes. The small GTPase ARF6 (ADP-ribosylation factor 6) has a central role in regulating membrane traffic and actin dynamics, and its activity has been demonstrated to be involved in neurite elaboration. EFA6A has been shown to act as a guanine nucleotide exchange factor (GEF) for ARF6. Here, we report that two distinct isoforms of the EFA6A gene are expressed in murine neural tissue: a long isoform of 1025 amino acids (EFA6A), and a short isoform of 393 amino acids (EFA6As). EFA6A encompasses proline-rich regions, a Sec7 domain (mediating GEF activity on ARF6), a PH domain, and a C-terminal region with coiled-coil motifs. EFA6As lacks the Sec7 domain, and it comprises the PH domain and the C-terminal region. The transcript encoding EFA6As is the result of alternative promoter usage. EFA6A and EFA6As have distinct biological activities: upon overexpression in HeLa cells, EFA6A induces membrane ruffles, whereas EFA6As gives rise to cell elongation; in primary cortical neurons EFA6A promotes neurite extension, whereas EFA6As induces dendrite branching. Our findings suggest that EFA6A could participate in neuronal morphogenesis through the regulated expression of two functionally distinct isoforms.
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Affiliation(s)
- Cristina Sironi
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy
| | - Tambet Teesalu
- Vascular Mapping Center, Burnham Institute for Medical Research at University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Anna Muggia
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy
| | - Gabriele Fontana
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy
| | - Fortunata Marino
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy
| | - Sara Savaresi
- Department of Biochemistry, University of Zürich, Winterthurer Strasse 190, 8057 Zürich, CH, Switzerland
| | - Daniela Talarico
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy
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Localization of EFA6A, a guanine nucleotide exchange factor for ARF6, in spermatogenic cells of testes of adult mice. J Mol Histol 2008; 40:77-80. [PMID: 19085064 DOI: 10.1007/s10735-008-9207-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2008] [Accepted: 11/26/2008] [Indexed: 11/27/2022]
Abstract
ADP ribosylation factors (ARFs) of small GTPase are molecular switches regulating various membrane dynamics. Among them, ARF6 has recently been highlighted because of its function to facilitate the interaction between the cytoskeleton and the plasma membrane. Each ARFs has its preferable or even specific guanine nucleotide exchange factors (GEFs) as its activators. According to our previous RT-PCR analysis, EFA6A, a guanine nucleotide exchange factor for ARF6, was restrictedly expressed in the brain, retina and testis. Different from previous studies on neurons, EFA6A, a guanine nucleotide exchange factor for ARF6, was first shown to be localized intensely in nuclei of spermatocytes of adult mouse testes in the present immunohistochemical study. This suggests a possible involvement of EFA6A-ARF6 signaling in the karyokinesis and cytokinesis.
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Reiner C, Nathanson NM. The internalization of the M2 and M4 muscarinic acetylcholine receptors involves distinct subsets of small G-proteins. Life Sci 2008; 82:718-27. [PMID: 18295803 DOI: 10.1016/j.lfs.2008.01.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2007] [Revised: 12/13/2007] [Accepted: 01/14/2008] [Indexed: 10/22/2022]
Abstract
Multiple mechanisms exist for the endocytosis of receptors from the cell surface. While the M1, M3, and M4 subtypes of muscarinic acetylcholine receptor and M4 receptors transduce their signals through the same second messengers but internalize though different pathways, we tested the ability of several small G-proteins to regulate the agonist-induced endocytosis of M2 and M4 in JEG-3 human choriocarcinoma cells. Dominant-negative Rab5 as well as both wild-type and dominant-negative Rab11 inhibited M4 but not M2 endocytosis. In contrast, a dominant-negative Arf6 as well as wild-type Rab22 increased M2 but not M4 endocytosis. We used immunocytochemistry to show that in unstimulated cells, the M2 and M4 receptors co-localize on the cell surface, whereas after stimulation M2 and M4 are in distinct vesicular compartments. In this study, we demonstrate that agonist-induced internalization of the M2 receptor utilizes an Arf6, Rab22 dependent pathway, while the M4 receptor undergoes agonist-induced internalization through a Rab5, Rab11 dependent pathway. Additionally, we show that Rab15 and RhoA are not involved in either pathway in JEG-3 cells.
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Affiliation(s)
- Cindy Reiner
- Department of Pharmacology, University of Washington, Seattle, WA 98195, United States
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El Hage T, Merlen C, Fabrega S, Authier F. Role of receptor-mediated endocytosis, endosomal acidification and cathepsin D in cholera toxin cytotoxicity. FEBS J 2007; 274:2614-29. [PMID: 17451437 DOI: 10.1111/j.1742-4658.2007.05797.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Using the in situ liver model system, we have recently shown that, after cholera toxin binding to hepatic cells, cholera toxin accumulates in a low-density endosomal compartment, and then undergoes endosomal proteolysis by the aspartic acid protease cathepsin-D [Merlen C, Fayol-Messaoudi D, Fabrega S, El Hage T, Servin A, Authier F (2005) FEBS J272, 4385-4397]. Here, we have used a subcellular fractionation approach to address the in vivo compartmentalization and cytotoxic action of cholera toxin in rat liver parenchyma. Following administration of a saturating dose of cholera toxin to rats, rapid endocytosis of both cholera toxin subunits was observed, coincident with massive internalization of both the 45 kDa and 47 kDa Gsalpha proteins. These events coincided with the endosomal recruitment of ADP-ribosylation factor proteins, especially ADP-ribosylation factor-6, with a time course identical to that of toxin and the A subunit of the stimulatory G protein (Gsalpha) translocation. After an initial lag phase of 30 min, these constituents were linked to NAD-dependent ADP-ribosylation of endogenous Gsalpha, with maximum accumulation observed at 30-60 min postinjection. Assessment of the subsequent postendosomal fate of internalized Gsalpha revealed sustained endolysosomal transfer of the two Gsalpha isoforms. Concomitantly, cholera toxin increased in vivo endosome acidification rates driven by the ATP-dependent H(+)-ATPase pump and in vitro vacuolar acidification in hepatoma HepG2 cells. The vacuolar H(+)-ATPase inhibitor bafilomycin and the cathepsin D inhibitor pepstatin A partially inhibited, both in vivo and in vitro, the cAMP response to cholera toxin. This cathepsin D-dependent action of cholera toxin under the control of endosomal acidity was confirmed using cellular systems in which modification of the expression levels of cathepsin D, either by transfection of the cathepsin D gene or small interfering RNA, was followed by parallel changes in the cytotoxic response to cholera toxin. Thus, in hepatic cells, a unique endocytic pathway was revealed following cholera toxin administration, with regulation specificity most probably occurring at the locus of the endosome and implicating endosomal proteases, such as cathepsin D, as well as organelle acidification.
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Affiliation(s)
- Tatiana El Hage
- INSERM, U756; and Université Paris-Sud, Faculté de Pharmacie, Châtenay, Malabry, France
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Johnson MS, Robertson DN, Holland PJ, Lutz EM, Mitchell R. Role of the conserved NPxxY motif of the 5-HT2A receptor in determining selective interaction with isoforms of ADP-ribosylation factor (ARF). Cell Signal 2006; 18:1793-800. [PMID: 16545942 DOI: 10.1016/j.cellsig.2006.02.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2005] [Revised: 02/01/2006] [Accepted: 02/03/2006] [Indexed: 11/25/2022]
Abstract
In this study we have shown that N376 to D mutation in the conserved NPxxY motif within the carboxy terminal tail domain (CT) of the 5-HT2A receptor alters the binding preference of GST-fusion protein constructs of the CT domain from ARF1 to an alternative isoform, ARF6. These findings were corroborated by experiments investigating co-immunoprecipitation of the wild type (WT) and N376D mutant of the 5-HT2A receptor with ARF1 or 6 or dominant negative ARF1/6 constructs co-expressed in COS7 cells. In functional assays of 5-HT-induced phospholipase D (PLD) activation responses of the WT receptor were inhibited by a dominant negative mutant of ARF1 but not ARF6, whereas responses of the N376D mutant were strongly inhibited by negative mutant ARF6. No equivalent effect of the ARF mutants was seen on phospholipase C activation. In experiments assaying 5-HT-induced increases in [35S]GTPgammaS binding to ARF 1/6 immunoprecipitates as a measure of ARF activation, increased ARF6 activation was seen only with the mutant receptor. When cellular PLD responses of other NPxxY- or a DPxxY-containing GPCRs were measured in the presence of dominant negative ARF1/6 constructs, the majority, but not all, fitted the pattern exemplified by the 5-HT2A receptor and its N376D mutant. These data suggest that the presence of the N or a D in this highly conserved motif is an important, but not exclusive, determinant of which ARF isoform interacts with the GPCR.
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Affiliation(s)
- Melanie S Johnson
- Membrane Biology Interdisciplinary Research Group, Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, EH8 9XD, UK
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15
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Schweitzer JK, D'Souza-Schorey C. A requirement for ARF6 during the completion of cytokinesis. Exp Cell Res 2005; 311:74-83. [PMID: 16181626 DOI: 10.1016/j.yexcr.2005.07.033] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2005] [Revised: 07/14/2005] [Accepted: 07/25/2005] [Indexed: 12/20/2022]
Abstract
During cancer development, coordinated changes in cell motility and cell cycle progression are required for the gradual transformation of normal cells into cancer cells. Previous studies have shown that ARF6 is a critical regulator of epithelial cell integrity and motility via its role in membrane movement and actin-based cytoskeletal remodeling. Recently, we have found that ARF6 also plays a role during cell division. It localizes to the cleavage furrow and midbody of cells during mitosis, and its activity is regulated during cytokinesis. Here, we investigate the requirement for ARF6 during mitosis and find that depletion of ARF6 using RNA interference disrupts the completion of cytokinesis. This finding demonstrates that ARF6 is essential during the final stages of cytokinesis. In addition, we have identified Ku70, a DNA-binding protein that is required for DNA damage repair, as a new ARF6-interacting protein and found that it is part of a complex with ARF6, especially during mitosis. These results clarify the importance of ARF6 activity during cytokinesis and begin to reveal other molecules that may contribute to the function of ARF6.
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Affiliation(s)
- Jill Kuglin Schweitzer
- Department of Biological Sciences and the Walther Cancer Institute, University of Notre Dame, 145 Galvin Life Science Bldg, Notre Dame, IN 46556-0369, USA
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16
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Hashimoto S, Onodera Y, Hashimoto A, Tanaka M, Hamaguchi M, Yamada A, Sabe H. Requirement for Arf6 in breast cancer invasive activities. Proc Natl Acad Sci U S A 2004; 101:6647-52. [PMID: 15087504 PMCID: PMC404099 DOI: 10.1073/pnas.0401753101] [Citation(s) in RCA: 216] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2003] [Indexed: 11/18/2022] Open
Abstract
In most human breast cancer cell lines, there is a direct correlation between their in vivo invasive phenotypes and in vitro invasion activities. Here, we found that ADP-ribosylation factor 6 (Arf6) is localized at the invadopodia of the cultured breast cancer cells MDA-MB-231, and its suppression by a small-interfering RNA duplex effectively blocks the invasive activities of the cells, such as invadopodia formation, localized matrix degradation and Matrigel transmigration but not the cell-adhesion activity. We also found that the GTP hydrolysis-defective mutant Arf6(Q67L) and the GTP-binding defective mutant Arf6(T27N) both blocked these invasive activities but not cell adhesion, suggesting the necessity of continued activation and cycling of the Arf6 GTPase cycle in invasion. Among the different human breast cancer cell lines that we examined, cell lines with high invasive activities expressed higher amounts of Arf6 protein than those in weakly invasive and noninvasive cell lines, although no notable correlation was found between Arf6 mRNA expression levels and invasive activities. Moreover, Matrigel-transmigration activity of all of these invasive cells was blocked effectively by an Arf6 small-interfering RNA duplex. Hence, Arf6 appears to be an integral component of breast cancer invasive activities, and we propose that Arf6 and the intracellular machinery regulating Arf6 during invasion should be considered as therapeutic targets for the prevention of breast cancer invasion.
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Affiliation(s)
- Shigeru Hashimoto
- Department of Molecular Biology, Osaka Bioscience Institute, Osaka 565-0874, Japan
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17
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El-Annan J, Brown D, Breton S, Bourgoin S, Ausiello DA, Marshansky V. Differential expression and targeting of endogenous Arf1 and Arf6 small GTPases in kidney epithelial cells in situ. Am J Physiol Cell Physiol 2004; 286:C768-78. [PMID: 14684384 DOI: 10.1152/ajpcell.00250.2003] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
ADP-ribosylation factors (Arfs) are small GTPases that regulate vesicular trafficking in exo- and endocytotic pathways. As a first step in understanding the role of Arfs in renal physiology, immunocytochemistry and Western blotting were performed to characterize the expression and targeting of Arf1 and Arf6 in epithelial cells in situ. Arf1 and Arf6 were associated with apical membranes and subapical vesicles in proximal tubules, where they colocalized with megalin. Arf1 was also apically expressed in the distal tubule, connecting segment, and collecting duct (CD). Arf1 was abundant in intercalated cells (IC) and colocalized with V-ATPase in A-IC (apical) and B-IC (apical and/or basolateral). In contrast, Arf6 was associated exclusively with basolateral membranes and vesicles in the CD. In the medulla, basolateral Arf6 was detectable mainly in A-IC. Expression in principal cells became weaker throughout the outer medulla, and Arf6 was not detectable in principal cells in the inner medulla. In some kidney epithelial cells Arf1 but not Arf6 was also targeted to a perinuclear patch, where it colocalized with TGN38, a marker of the trans-Golgi network. Quantitative Western blotting showed that expression of endogenous Arf1 was 26–180 times higher than Arf6. These data indicate that Arf GTPases are expressed and targeted in a cell- and membrane-specific pattern in kidney epithelial cells in situ. The results provide a framework on which to base and interpret future studies on the role of Arf GTPases in the multitude of cellular trafficking events that occur in renal tubular epithelial cells.
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Affiliation(s)
- Jaafar El-Annan
- Program in Membrane Biology and Renal Unit, Massachusetts General Hospital, Boston, MA 02129-2020, USA
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18
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Cox R, Mason-Gamer RJ, Jackson CL, Segev N. Phylogenetic analysis of Sec7-domain-containing Arf nucleotide exchangers. Mol Biol Cell 2004; 15:1487-505. [PMID: 14742722 PMCID: PMC379250 DOI: 10.1091/mbc.e03-06-0443] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The eukaryotic family of ADP-ribosylation factor (Arf) GTPases plays a key role in the regulation of protein trafficking, and guanine-nucleotide exchange is crucial for Arf function. Exchange is stimulated by members of another family of proteins characterized by a 200-amino acid Sec7 domain, which alone is sufficient to catalyze exchange on Arf. Here, we analyzed the phylogeny of Sec7-domain-containing proteins in seven model organisms, representing fungi, plants, and animals. The phylogenetic tree has seven main groups, of which two include members from all seven model systems. Three groups are specific for animals, whereas two are specific for fungi. Based on this grouping, we propose a phylogenetically consistent set of names for members of the Sec7-domain family. Each group, except for one, contains proteins with known Arf exchange activity, implying that all members of this family have this activity. Contrary to the current convention, the sensitivity of Arf exchange activity to the inhibitor brefeldin A probably cannot be predicted by group membership. Multiple alignment reveals group-specific domains outside the Sec7 domain and a set of highly conserved amino acids within it. Determination of the importance of these conserved elements in Arf exchange activity and other cellular functions is now possible.
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Affiliation(s)
- Randal Cox
- Department of Biochemistry, Laboratory for Molecular Biology, University of Illinois at Chicago, Chicago, Illinois 60607, USA
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19
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Riley KN, Maldonado AE, Tellier P, D'Souza-Schorey C, Herman IM. Betacap73-ARF6 interactions modulate cell shape and motility after injury in vitro. Mol Biol Cell 2003; 14:4155-61. [PMID: 14517325 PMCID: PMC207007 DOI: 10.1091/mbc.e02-11-0726] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2002] [Revised: 05/13/2003] [Accepted: 05/30/2003] [Indexed: 11/11/2022] Open
Abstract
To understand the role that ARF6 plays in regulating isoactin dynamics and cell motility, we transfected endothelial cells (EC) with HA-tagged ARF6: the wild-type form (WT), a constitutively-active form unable to hydrolyze GTP (Q67L), and two dominant-negative forms, which are either unable to release GDP (T27N) or fail to bind nucleotide (N122I). Motility was assessed by digital imaging microscopy before Western blot analysis, coimmunoprecipitation, or colocalization studies using ARF6, beta-actin, or beta-actin-binding protein-specific antibodies. EC expressing ARF6-Q67L spread and close in vitro wounds at twice the control rates. EC expressing dominant-negative ARF6 fail to develop a leading edge, are unable to ruffle their membranes (N122I), and possess arborized processes. Colocalization studies reveal that the Q67L and WT ARF6-HA are enriched at the leading edge with beta-actin; but T27N and N122I ARF6-HA are localized on endosomes together with the beta-actin capping protein, betacap73. Coimmunoprecipitation and Western blot analyses reveal the direct association of ARF6-HA with betacap73, defining a role for ARF6 in signaling cytoskeletal remodeling during motility. Knowledge of the role that ARF6 plays in orchestrating membrane and beta-actin dynamics will help to reveal molecular mechanisms regulating actin-based motility during development and disease.
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Affiliation(s)
- Kathleen N Riley
- Cell and Molecular Physiology, Tufts University School of Medicine, Boston, Massachusetts 62111, USA
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20
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Matsukawa J, Nakayama K, Nagao T, Ichijo H, Urushidani T. Role of ADP-ribosylation factor 6 (ARF6) in gastric acid secretion. J Biol Chem 2003; 278:36470-5. [PMID: 12860984 DOI: 10.1074/jbc.m305444200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ADP-ribosylation factor (ARF) proteins are monomeric GTPases that are essential for membrane transport and exocytosis in a number of secretory cells. We investigated ARF6, the activation of which is insensitive to brefeldin A, to determine whether it regulates membrane traffic in gastric parietal cells. ARF6 translocated from cytosol to tubulovesicle in the presence of GTPgammaS, a potential inhibitor of acid secretion in permeabilized cells, whereas under the Mg2+-chelated condition where activity of ARF-GTPase activating protein is inhibited, ARF6 translocated to the apical secretory membrane. Immunohistochemical examination revealed that ARF6 mainly located in parietal cell within the gastric glands, and it translocated from the cytosol to the intracellular canaliculi when the glands were stimulated. These results indicated that the distribution of ARF6 between cytosol and the two different membranes was regulated by its GTPase activity. In cultured gastric glands infected with adenovirus expressing ARF6 Q67L, a mutant lacking GTP hydrolysis activity, gastric acid secretion was inhibited. These results suggest that ARF6 regulates gastric acid secretion in parietal cell and that the GTP hydrolysis cycle of ARF6 is essential for the activation pathway.
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Affiliation(s)
- Jun Matsukawa
- Laboratory of Cell Signaling, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
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21
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Li HS, Shome K, Rojas R, Rizzo MA, Vasudevan C, Fluharty E, Santy LC, Casanova JE, Romero G. The guanine nucleotide exchange factor ARNO mediates the activation of ARF and phospholipase D by insulin. BMC Cell Biol 2003; 4:13. [PMID: 12969509 PMCID: PMC212319 DOI: 10.1186/1471-2121-4-13] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2003] [Accepted: 09/11/2003] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Phospholipase D (PLD) is involved in many signaling pathways. In most systems, the activity of PLD is primarily regulated by the members of the ADP-Ribosylation Factor (ARF) family of GTPases, but the mechanism of activation of PLD and ARF by extracellular signals has not been fully established. Here we tested the hypothesis that ARF-guanine nucleotide exchange factors (ARF-GEFs) of the cytohesin/ARNO family mediate the activation of ARF and PLD by insulin. RESULTS Wild type ARNO transiently transfected in HIRcB cells was translocated to the plasma membrane in an insulin-dependent manner and promoted the translocation of ARF to the membranes. ARNO mutants: DeltaCC-ARNO and CC-ARNO were partially translocated to the membranes while DeltaPH-ARNO and PH-ARNO could not be translocated to the membranes. Sec7 domain mutants of ARNO did not facilitate the ARF translocation. Overexpression of wild type ARNO significantly increased insulin-stimulated PLD activity, and mutations in the Sec7 and PH domains, or deletion of the PH or CC domains inhibited the effects of insulin. CONCLUSIONS Small ARF-GEFs of the cytohesin/ARNO family mediate the activation of ARF and PLD by the insulin receptor.
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Affiliation(s)
- Hai-Sheng Li
- Departments of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA
| | - Kuntala Shome
- Departments of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA
| | - Raúl Rojas
- Departments of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA
- Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA
| | - Megan A Rizzo
- Departments of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA
| | - Chandrasekaran Vasudevan
- Departments of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA
| | - Eric Fluharty
- Departments of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA
| | - Lorraine C Santy
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22908 USA
| | - James E Casanova
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22908 USA
| | - Guillermo Romero
- Departments of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261 USA
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22
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Mitchell R, Robertson DN, Holland PJ, Collins D, Lutz EM, Johnson MS. ADP-ribosylation factor-dependent phospholipase D activation by the M3 muscarinic receptor. J Biol Chem 2003; 278:33818-30. [PMID: 12799371 DOI: 10.1074/jbc.m305825200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G protein-coupled receptors can potentially activate phospholipase D (PLD) by a number of routes. We show here that the native M3 muscarinic receptor in 1321N1 cells and an epitope-tagged M3 receptor expressed in COS7 cells substantially utilize an ADP-ribosylation factor (ARF)-dependent route of PLD activation. This pathway is activated at the plasma membrane but appears to be largely independent of G, phospholipase C, Ca2+ q/11, protein kinase C, tyrosine kinases, and phosphatidyl inositol 3-kinase. We report instead that it involves physical association of ARF with the M3 receptor as demonstrated by co-immunoprecipitation and by in vitro interaction with a glutathione S-transferase fusion protein of the receptor's third intracellular loop domain. Experiments with mutant constructs of ARF1/6 and PLD1/2 indicate that the M3 receptor displays a major ARF1-dependent route of PLD1 activation with an additional ARF6-dependent pathway to PLD1 or PLD2. Examples of other G protein-coupled receptors assessed in comparison display alternative pathways of protein kinase C- or ARF6-dependent activation of PLD2.
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Affiliation(s)
- Rory Mitchell
- Medical Research Council Membrane and Adapter Proteins Co-operative Group, Membrane Biology Interdisciplinary Research Group, School of Biomedical and Clinical Laboratory Sciences, University of Edinburgh, EH8 9XD, United Kingdom.
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23
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Krauss M, Kinuta M, Wenk MR, De Camilli P, Takei K, Haucke V. ARF6 stimulates clathrin/AP-2 recruitment to synaptic membranes by activating phosphatidylinositol phosphate kinase type Igamma. J Cell Biol 2003; 162:113-24. [PMID: 12847086 PMCID: PMC2172713 DOI: 10.1083/jcb.200301006] [Citation(s) in RCA: 227] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Clathrin-mediated endocytosis of synaptic vesicle membranes involves the recruitment of clathrin and AP-2 adaptor complexes to the presynaptic plasma membrane. Phosphoinositides have been implicated in nucleating coat assembly by directly binding to several endocytotic proteins including AP-2 and AP180. Here, we show that the stimulatory effect of ATP and GTPgammaS on clathrin coat recruitment is mediated at least in part by increased levels of PIP2. We also provide evidence for a role of ADP-ribosylation factor 6 (ARF6) via direct stimulation of a synaptically enriched phosphatidylinositol 4-phosphate 5-kinase type Igamma (PIPKIgamma), in this effect. These data suggest a model according to which activation of PIPKIgamma by ARF6-GTP facilitates clathrin-coated pit assembly at the synapse.
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Affiliation(s)
- Michael Krauss
- Department of Biochemistry II, Zentrum für Biochemie und Molekulare Zellbiologie, University of Göttingen, D-37073 Göttingen, Germany
| | - Masahiro Kinuta
- Department of Neuroscience, Okayama University Graduate School of Medicine and Dentistry, Okayama 700-8558, Japan
| | - Markus R. Wenk
- Department of Cell Biology and Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510
| | - Pietro De Camilli
- Department of Cell Biology and Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510
| | - Kohji Takei
- Department of Neuroscience, Okayama University Graduate School of Medicine and Dentistry, Okayama 700-8558, Japan
| | - Volker Haucke
- Department of Biochemistry II, Zentrum für Biochemie und Molekulare Zellbiologie, University of Göttingen, D-37073 Göttingen, Germany
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24
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Palacios F, D'Souza-Schorey C. Modulation of Rac1 and ARF6 activation during epithelial cell scattering. J Biol Chem 2003; 278:17395-400. [PMID: 12609992 DOI: 10.1074/jbc.m300998200] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Epithelial cell scattering encompasses the dissolution of intercellular junctions, cell-cell dissociation, cell spreading, and motility. The Rac1 and ARF6 GTPases have been shown to regulate one or more of these aforementioned processes. In fact, activated Rac1 has been shown to promote cell-cell adhesion as well as to enhance cell motility, leading to conflicting reports on the effect of Rac1 activation on epithelial cell motility. In this study, we have examined the activation profiles of endogenous Rac1 and ARF6 during the sequential stages of epithelial cell scattering. Using Madin-Darby canine kidney cells treated with hepatocyte growth factor/scatter factor or cell lines stably expressing activated v-Src, we show that Rac1 and ARF6 exhibit distinct activation profiles during cell scattering. We have found that an initial ARF6-dependent decrease in the levels of Rac1-GTP is necessary to induce cell-cell dissociation. This is followed by a steady increase in Rac1 and ARF6 activation and cell migration. In sum, this study documents the progression of ARF6 and Rac1 activities during epithelial cell scattering.
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Affiliation(s)
- Felipe Palacios
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556-0369, USA
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25
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Lin CY, Li CC, Huang PH, Lee FJS. A developmentally regulated ARF-like 5 protein (ARL5), localized to nuclei and nucleoli, interacts with heterochromatin protein 1. J Cell Sci 2002; 115:4433-45. [PMID: 12414990 DOI: 10.1242/jcs.00123] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
ARF-like proteins (ARLs) are distinct group of members of the ARF family of Ras-related GTPases. Although ARLs are very similar in primary structure to ARFs, their functions remain unclear. We cloned mouse (m) and human (h) ARL5 cDNAs to characterize the protein products and their molecular properties. mARL5 mRNA was more abundant in liver than in other adult tissues tested. mARL5, similar to mARL4, was developmentally regulated and localized to nuclei. hARL5 interacted with importin-alpha through its C-terminal bipartite nuclear localization signal. When expressed in COS-7 cells, mutant hARL5(T35N), which is predicted to be GDP bound, was concentrated in nucleoli. The N-terminus of hARL5, like that of ARF, was myristoylated. Yeast two-hybrid screening and in vitro protein-interaction assays showed that hARL5(Q80L), predicted to be GTP bound, interacted with heterochromatin protein 1alpha (HP1alpha), which is known to be associated with telomeres as well as with heterochromatin, and acted as a transcriptional suppressor in mammalian cells. The interaction was reproduced in COS cells, where hARL5(Q80L) was co-immunoprecipitated with HP1alpha. hARL5 interaction with HP1alpha was dependent on the nucleotide bound, and required the MIR-like motif. Moreover, hARL5(Q80L), but not hARL5 lacking the MIR-like motif, was partly co-localized with overexpressed HP1alpha. Our findings suggest that developmentally regulated ARL5, with its distinctive nuclear/nucleolar localization and interaction with HP1alpha, may play a role(s) in nuclear dynamics and/or signaling cascades during embryonic development.
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Affiliation(s)
- Ching-Yi Lin
- Institute of Molecular Medicine, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan, Republic of China
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26
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Schweitzer JK, D'Souza-Schorey C. Localization and activation of the ARF6 GTPase during cleavage furrow ingression and cytokinesis. J Biol Chem 2002; 277:27210-6. [PMID: 12016212 DOI: 10.1074/jbc.m201569200] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ARF6 GTPase mediates cell shape changes in interphase cells through its effects on membrane cycling and actin remodeling. In this study, we focus our attention on the dynamics of cell division and present evidence supporting a novel role for ARF6 during cleavage furrow ingression and cytokinesis. We demonstrate that endogenous ARF6 redistributes during mitosis and concentrates near the cleavage furrow during telophase. Constitutively activated ARF6 localizes to the plasma membrane at the site of cleavage furrow ingression and midbody formation, and dominant negative ARF6 remains cytoplasmic. By using a novel pull-down assay for ARF6-GTP, we find an abrupt, but transient, increase in ARF6-GTP levels as cells progress through cytokinesis. Whereas high levels of expression of a GTPase-defective ARF6 mutant induce aberrant phenotypes in cells at cytokinesis, cells expressing low levels of ARF6 mutants do not display a significant mitotic delay or cytokinesis defect, presumably due to compensatory or redundant mechanisms that allow cytokinesis to proceed when the ARF6 GTPase cycle is disrupted. Finally, actin accumulation and phospholipid metabolism at the cleavage furrow are unchanged in cells expressing ARF6 mutants, suggesting that ARF6 may be involved in membrane remodeling during cytokinesis via effector pathways that are distinct from those operative in interphase cells.
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Affiliation(s)
- Jill Kuglin Schweitzer
- Department of Biological Sciences, Walther Cancer Institute, Galvin Life Sciences Building, University of Notre Dame, Notre Dame, IN 46556, USA
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27
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Skippen A, Jones DH, Morgan CP, Li M, Cockcroft S. Mechanism of ADP ribosylation factor-stimulated phosphatidylinositol 4,5-bisphosphate synthesis in HL60 cells. J Biol Chem 2002; 277:5823-31. [PMID: 11744730 DOI: 10.1074/jbc.m110274200] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) is required both as a substrate for the generation of lipid-derived second messengers as well as an intact lipid for many aspects of cell signaling, endo- and exocytosis, and reorganization of the cytoskeleton. ADP ribosylation factor (ARF) proteins regulate PI(4,5)P(2) synthesis, and here we have examined whether this is due to direct activation of Type I phosphatidylinositol 4-phosphate (PIP) 5-kinase or indirectly by phosphatidate (PA) derived from phospholipase D (PLD) in HL60 cells. ARF1 and ARF6 are both expressed in HL60 cells and can be depleted from the cells by permeabilization. Both ARFs increased the levels of PIP(2) (PI(4,5)P(2), PI(3,5)P(2), or PI(3,4)P(2) isomers) at the expense of PIP when added back to permeabilized cells. The PIP(2) could be hydrolyzed by phospholipase C, identifying it as PI(4,5)P(2). However, the ARF1-stimulated pool of PI(4,5)P(2) was accessible to the phospholipase C more efficiently in the presence of phosphatidylinositol transfer protein-alpha. To examine the role of PLD in the regulation of PI(4,5)P(2) synthesis, we used butanol to diminish the PLD-derived PA. PI(4,5)P(2) synthesis stimulated by ARF1 was not blocked by 0.5% butanol but could be blocked by 1.5% butanol. Although 0.5% butanol was optimal for maximal transphosphatidylation, PA production was still detectable. In contrast, 1.5% butanol was found to inhibit the activation of PLD by ARF1 and also decrease PIP levels by 50%. Thus the toxicity of 1.5% butanol prevented us from concluding whether PA was an important factor in raising PI(4,5)P(2) levels. To circumvent the use of alcohols, an ARF1 point mutant was identified (N52R-ARF1) that could selectively activate PIP 5-kinase alpha activity but not PLD activity. N52R-ARF1 was still able to increase PI(4,5)P(2) levels but at reduced efficiency. We therefore conclude that both PA derived from the PLD pathway and ARF proteins, by directly activating PIP 5-kinase, contribute to the regulation of PI(4,5)P(2) synthesis at the plasma membrane in HL60 cells.
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Affiliation(s)
- Alison Skippen
- Department of Physiology, University College London, London WC1E 6JJ, United Kingdom
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28
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Salvador LM, Mukherjee S, Kahn RA, Lamm ML, Fazleabas AT, Maizels ET, Bader MF, Hamm H, Rasenick MM, Casanova JE, Hunzicker-Dunn M. Activation of the luteinizing hormone/choriogonadotropin hormone receptor promotes ADP ribosylation factor 6 activation in porcine ovarian follicular membranes. J Biol Chem 2001; 276:33773-81. [PMID: 11448949 DOI: 10.1074/jbc.m101498200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previously we demonstrated in a cell-free ovarian follicular plasma membrane model that agonist-dependent desensitization of the luteinizing hormone/choriogonadotropin receptor (LH/CG R) is GTP-dependent, mimicked by the addition of ADP-ribosylation factor (ARF) nucleotide binding site opener, which acts as a guanine nucleotide exchange factor for ARFs 1 and 6, and selectively inhibited by synthetic N-terminal ARF6 peptides. We therefore sought direct evidence that activation of the LH/CG R promotes activation of ARF1 and/or ARF6. Using a classic ARF activation assay, the cholera toxin-catalyzed ADP-ribosylation of G alpha(s), results show that LH/CG R activation stimulates an ARF protein by a brefeldin A-independent mechanism. Synthetic N-terminal inhibitory ARF6 but not ARF1 peptide blocks LH/CG R-stimulated ARF activity. LH/CG R activation also promotes the binding of a photoaffinity GTP analog to a protein that migrates on one- and two-dimensional polyacrylamide gel electrophoresis with ARF6. These results suggest that ARF6 is the predominant ARF activated by the LH/CG R. To activate ARF6, the LH/CG R does not appear to signal through the C-terminal regions of G alpha(i) or G alpha(q) or through the second or third intracellular loops or the N terminus of the cytoplasmic tail of the LH/CG R. Although exogenous recombinant ARNO promotes only a small increase in ARF6 activation in the presence of activated LH/CG R, hCG-stimulated ARF6 activation is reduced to basal levels by catalytically inactive ARF nucleotide binding-site opener. These results provide direct evidence that LH/CG R activation leads to the activation of membrane-delimited ARF6.
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Affiliation(s)
- L M Salvador
- Department of Cell and Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611, USA
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29
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Palacios F, Price L, Schweitzer J, Collard JG, D’Souza-Schorey C. An essential role for ARF6-regulated membrane traffic in adherens junction turnover and epithelial cell migration. EMBO J 2001; 20:4973-86. [PMID: 11532961 PMCID: PMC125602 DOI: 10.1093/emboj/20.17.4973] [Citation(s) in RCA: 242] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
We describe a novel role for the ARF6 GTPase in the regulation of adherens junction (AJ) turnover in MDCK epithelial cells. Expression of a GTPase-defective ARF6 mutant, ARF6(Q67L), led to a loss of AJs and ruffling of the lateral plasma membrane via mechanisms that were mutually exclusive. ARF6-GTP-induced AJ disassembly did not require actin remodeling, but was dependent on the internalization of E-cadherin into the cytoplasm via vesicle transport. ARF6 activation was accompanied by increased migratory potential, and treatment of cells with hepatocyte growth factor (HGF) induced the activation of endogenous ARF6. The effect of ARF6(Q67L) on AJs was specific since ARF6 activation did not perturb tight junction assembly or cell polarity. In contrast, dominant-negative ARF6, ARF6(T27N), localized to AJs and its expression blocked cell migration and HGF-induced internalization of cadherin-based junctional components into the cytoplasm. Finally, we show that ARF6 exerts its role downstream of v-Src activation during the disassembly of AJs. These findings document an essential role for ARF6- regulated membrane traffic in AJ disassembly and epithelial cell migration.
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Affiliation(s)
| | - Leo Price
- Department of Biological Sciences and the Walther Cancer Institute, University of Notre Dame, Notre Dame, IN 46556-0369 and
The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands Corresponding author e-mail: D’
| | | | - John G. Collard
- Department of Biological Sciences and the Walther Cancer Institute, University of Notre Dame, Notre Dame, IN 46556-0369 and
The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands Corresponding author e-mail: D’
| | - Crislyn D’Souza-Schorey
- Department of Biological Sciences and the Walther Cancer Institute, University of Notre Dame, Notre Dame, IN 46556-0369 and
The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands Corresponding author e-mail: D’
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30
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Macia E, Chabre M, Franco M. Specificities for the small G proteins ARF1 and ARF6 of the guanine nucleotide exchange factors ARNO and EFA6. J Biol Chem 2001; 276:24925-30. [PMID: 11342560 DOI: 10.1074/jbc.m103284200] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ARF1 and ARF6 are distant members of the ADP-ribosylation factor (ARF) small G-protein subfamily. Their distinct cellular functions must result from specificity of interaction with different effectors and regulators, including guanine nucleotide exchange factors (GEFs). ARF nucleotide-binding site opener (ARNO), and EFA6 are analogous ARF-GEFs, both comprising a catalytic "Sec7" domain and a pleckstrin homology domain. In vivo ARNO, like ARF1, is mostly cytosolic, with minor localizations at the Golgi and plasma membrane; EFA6, like ARF6, is restricted to the plasma membrane. However, depending on conditions, ARNO appears active on ARF6 as well as on ARF1. Here we analyze the origin of these ARF-GEF selectivities. In vitro, in the presence of phospholipid membranes, ARNO activates ARF1 preferentially and ARF6 slightly, whereas EFA6 activates ARF6 exclusively; the stimulation efficiency of EFA6 on ARF6 is comparable with that of ARNO on ARF1. These selectivities are determined by the GEFs Sec7 domains alone, without the pleckstrin homology and N-terminal domains, and by the ARF core domains, without the myristoylated N-terminal helix; they are not modified upon permutation between ARF1 and ARF6 of the few amino acids that differ within the switch regions. Thus selectivity for ARF1 or ARF6 must depend on subtle folding differences between the ARFs switch regions that interact with the Sec7 domains.
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Affiliation(s)
- E Macia
- Institut de Pharmacologie Moléculaire et Cellulaire, CNRS-UMR 6097, 660 Route des Lucioles, 06560 Valbonne Sophia-Antipolis, France
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31
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Donaldson JG, Radhakrishna H. Expression and properties of ADP-ribosylation factor (ARF6) in endocytic pathways. Methods Enzymol 2001; 329:247-56. [PMID: 11210541 DOI: 10.1016/s0076-6879(01)29085-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- J G Donaldson
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892-0301, USA
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32
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Lin CY, Huang PH, Liao WL, Cheng HJ, Huang CF, Kuo JC, Patton WA, Massenburg D, Moss J, Lee FJ. ARL4, an ARF-like protein that is developmentally regulated and localized to nuclei and nucleoli. J Biol Chem 2000; 275:37815-23. [PMID: 10980193 DOI: 10.1074/jbc.m002470200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ADP-ribosylation factors (ARFs) are highly conserved approximately 20-kDa guanine nucleotide-binding proteins that participate in both exocytic and endocytic vesicular transport pathways via mechanisms that are only partially understood. Although several ARF-like proteins (ARLs) are known, their biological functions remain unclear. To characterize its molecular properties, we cloned mouse and human ARL4 (mARL4 and hARL4) cDNA. The appearance of mouse ARL4 mRNA during embryonic development coincided temporally with the sequential formation of somites and the establishment of brain compartmentation. Using ARL4-specific antibody for immunofluorescence microscopy, we observed that endogenous mARL4 in cultured Sertoli and neuroblastoma cells was mainly concentrated in nuclei. When expressed in COS7 cells, ARL4-T34N mutant, predicted to exist with GDP bound, was concentrated in nucleoli. Yeast two-hybrid screening and in vitro protein-interaction assays showed that hARL4 interacted with importin-alpha through its C-terminal NLS region and that the interaction was not nucleotide-dependent. Like ARL2 and -3, recombinant hARL4 did not enhance cholera toxin-catalyzed auto-ADP-ribosylation. Its binding of guanosine 5'-O-(thiotriphosphate) was modified by phospholipid and detergent, and the N terminus of hARL4, like that of ARF, was myristoylated. Our findings suggest that ARL4, with its distinctive nuclear/nucleolar localization and pattern of developmental expression, may play a unique role(s) in neurogenesis and somitogenesis during embryonic development and in the early stages of spermatogenesis in adults.
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Affiliation(s)
- C Y Lin
- Institute of Molecular Medicine and Institute of Pathology, College of Medicine, National Taiwan University, Taipei, Taiwan, Republic of China
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33
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Le Stunff H, Dokhac L, Bourgoin S, Bader MF, Harbon S. Phospholipase D in rat myometrium: occurrence of a membrane-bound ARF6 (ADP-ribosylation factor 6)-regulated activity controlled by betagamma subunits of heterotrimeric G-proteins. Biochem J 2000; 352 Pt 2:491-9. [PMID: 11085943 PMCID: PMC1221481 DOI: 10.1042/0264-6021:3520491] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Both protein kinase C and protein tyrosine kinases have been shown to be involved in phospholipase D (PLD) activation in intact rat myometrium [Le Stunff, Dokhac and Harbon (2000) J. Pharmacol. Exp. Ther. 292, 629-637]. In this study we assessed the involvement of monomeric G-proteins in PLD activation in a cell-free system derived from myometrial tissue. Both the PLD1 and PLD2 isoforms were detected. Two forms of PLD activity, essentially membrane-bound, were found in myometrial preparations. One form was stimulated by oleate and insensitive to guanosine 5'-[gamma-thio] triphosphate (GTP[S]). The second required ammonium sulphate to be detected and was stimulated by GTP[S]. ADP-ribosylation factors (ARF1 and ARF6) and RhoA were immunodetected in myometrial preparations. ARF1 and RhoA were present in the membrane and cytosolic fractions whereas ARF6 was detected exclusively in the membrane fraction. A synthetic myristoylated peptide corresponding to the N-terminal domain of ARF6 [myrARF6((2-13))] totally abolished PLD activation in the presence of ammonium sulphate and GTP[S], whereas myrARF1((2-17)) and the inhibitory GDP/GTP-exchange factor, Rho GDI, did not. These data are consistent with a membrane-bound ARF6-regulated PLD activity. Finally, the stimulation of PLD by ARF6 was inhibited by AlF(-)(4) and this inhibition was counteracted by the fusion protein glutathione S-transferase-beta-adrenergic receptor kinase 1 (495-689) and by the QEHA peptide (from adenylate cyclase ACII), which act as G-protein betagamma-subunit scavengers. It is concluded that G-protein subunits betagamma are involved in a pathway modulating PLD activation by ARF6, illustrating cross-talk between heterotrimeric and monomeric G-proteins.
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Affiliation(s)
- H Le Stunff
- Signalisation et Régulations Cellulaires, CNRS UMR 8619, Bâtiment 432, Université Paris-Sud, 91405 Orsay Cedex, France
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34
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Vitale N, Ferrans VJ, Moss J, Vaughan M. Identification of lysosomal and Golgi localization signals in GAP and ARF domains of ARF domain protein 1. Mol Cell Biol 2000; 20:7342-52. [PMID: 10982851 PMCID: PMC86288 DOI: 10.1128/mcb.20.19.7342-7352.2000] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
ADP ribosylation factors (ARFs) are approximately 20-kDa guanine nucleotide-binding proteins that activate cholera toxin and phospholipase D and are critical components of vesicular trafficking pathways. ARF domain protein 1 (ARD1), a member of the ARF superfamily, contains a 46-kDa amino-terminal extension, which acts as a GTPase-activating protein (GAP) with activity towards its ARF domain. When overexpressed, ARD1 was associated with lysosomes and the Golgi apparatus. In agreement with this finding, lysosomal and Golgi membranes isolated from human liver by immunoaffinity contained native ARD1. ARD1, expressed as a green fluorescent fusion protein, was initially associated with the Golgi network and subsequently appeared on lysosomes, suggesting that ARD1 might undergo vectorial transport between the two organelles. Here we show by microscopic colocalization that GAP and ARF domains determine lysosomal and Golgi localization, respectively, consistent with the presence of more than one signal motif. Using truncated ARD1 molecules, expressed as green fluorescent fusion proteins, it was found that the signal for lysosomal localization was present in residues 301 to 402 of the GAP domain. Site-specific mutagenesis demonstrated that the sequence (369)KXXXQ(373) in the GAP domain was responsible for lysosomal localization. Association of ARD1 with the Golgi apparatus required tyrosine-based motifs. A green fluorescent fusion protein containing the QKQQQQF motif was partially associated with lysosomes, suggesting that this motif contains the information sufficient for lysosomal targeting. These results suggest that ARD1 is a multidomain protein with ARF and GAP regions, which contain Golgi and lysosomal localization signals, respectively, that could function in vesicular trafficking.
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Affiliation(s)
- N Vitale
- Pulmonary-Critical Care Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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35
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Al-Awar O, Radhakrishna H, Powell NN, Donaldson JG. Separation of membrane trafficking and actin remodeling functions of ARF6 with an effector domain mutant. Mol Cell Biol 2000; 20:5998-6007. [PMID: 10913182 PMCID: PMC86076 DOI: 10.1128/mcb.20.16.5998-6007.2000] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/1999] [Accepted: 05/15/2000] [Indexed: 11/20/2022] Open
Abstract
The ADP-ribosylation factor 6 (ARF6) GTPase has a dual function in cells, regulating membrane traffic and organizing cortical actin. ARF6 activation is required for recycling of the endosomal membrane back to the plasma membrane (PM) and also for ruffling at the PM induced by Rac. Additionally, ARF6 at the PM induces the formation of actin-containing protrusions. To identify sequences in ARF6 that are necessary for these distinct functions, we examined the behavior of a chimeric protein of ARF1 and ARF6. The 1-6 chimera (with the amino half of ARF1 and the carboxyl half of ARF6) localized like ARF6 in HeLa cells and moved between the endosome and PM, but it did not form protrusions, an ARF6 effector function. Two residues in the amino-terminal half of ARF6, Q37 and S38, when substituted into the 1-6 chimera allowed protrusion formation, whereas removal of these residues from ARF6 resulted in an inability to form protrusions. Interestingly, expression of 1-6 in cells selectively inhibited protrusions induced by wild-type ARF6 but had no effect on ARF6-regulated membrane movement or Rac-induced ruffling. Thus, we have uncoupled two functions of ARF6, one involved in membrane trafficking, which is necessary for Rac ruffling, and another involved in protrusion formation.
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Affiliation(s)
- O Al-Awar
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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36
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Ducret A, Desponts C, Desmarais S, Gresser MJ, Ramachandran C. A general method for the rapid characterization of tyrosine-phosphorylated proteins by mini two-dimensional gel electrophoresis. Electrophoresis 2000; 21:2196-208. [PMID: 10892730 DOI: 10.1002/1522-2683(20000601)21:11<2196::aid-elps2196>3.0.co;2-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Our preliminary results are reported in the investigation of the tyrosine phosphorylation cascade triggered by the stimulation of the insulin receptor in the adipocyte cell line 3T3-L1 using a mini two-dimensional gel electrophoresis approach. The minigel format, 8 x 10 cm, was found sufficiently resolving and reproducible to study complex biological samples while considerably increasing throughput and lowering costs compared to larger gel formats. Consequently, we used the minigel format to rapidly screen a large number of samples, of which only the most relevant were then analyzed by optimized, preparative two-dimensional gels. The accurate localization and relative quantification of tyrosine-phosphorylated proteins was performed using a nonradioactive triple labeling method. After transfer onto polyvinylidene difluoride (PVDF) membranes, proteins were stained with Sypro Ruby to verify the separation quality and to localize the general region of interest for immunostaining. The membranes were subsequently blocked with polyvinylpyrrolidone-40 and probed with the relevant antibodies for visualization of the phosphorylated proteins by chemiluminescence. Finally, membranes were stained with colloidal gold to obtain a pattern reminiscent of the silver staining of a polyacrylamide gel. We believe that the presented strategy can be generalized for any gel application in which a protein has to be detected and identified based on its immunoreactivity.
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Affiliation(s)
- A Ducret
- Merck Frosst Center for Therapeutic Research, Pointe-Claire-Dorval, Québec, Canada.
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37
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Ménétrey J, Macia E, Pasqualato S, Franco M, Cherfils J. Structure of Arf6-GDP suggests a basis for guanine nucleotide exchange factors specificity. NATURE STRUCTURAL BIOLOGY 2000; 7:466-9. [PMID: 10881192 DOI: 10.1038/75863] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Arf6 is an isoform of Arf that localizes at the periphery of the cell where it has an essential role in endocytotic pathways. Its function does not overlap with that of Arf1, although the two proteins share approximately 70% sequence identity and they have switch regions, whose conformation depends on the nature of the guanine nucleotide, with almost identical sequences. The crystal structure of Arf6-GDP at 2.3 A shows that it has a conformation similar to that of Arf1-GDP, which cannot bind membranes with high affinity. Significantly, the switch regions of Arf6 deviate by 2-5 A from those of Arf1. These differences are a consequence of the shorter N-terminal linker of Arf6 and of discrete sequence changes between Arf6 and Arf1. Mutational analysis shows that one of the positions which differs between Arf1 and Arf6 affects the configuration of the nucleotide binding site and thus the nucleotide binding properties of the Arf variant. Altogether, our results provide a structural basis for understanding how Arf1 and Arf6 can be distinguished by their guanine nucleotide exchange factors and suggest a model for the nucleotide/membrane cycle of Arf6.
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Affiliation(s)
- J Ménétrey
- Laboratoire d'Enzymologie et Biochimie Structurales, CNRS, Gif-sur-Yvette, France
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38
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Abstract
ARF proteins are important regulators of membrane dynamics and protein transport within the eukaryotic cell. The Sec7 domain is approximately 200 amino acids in size and stimulates guanine-nucleotide exchange on members of the ARF class of small GTPases. The members of one subclass of Sec7-domain proteins are direct targets of the secretion-inhibiting drug brefeldin A, which blocks the exchange reaction by trapping a reaction intermediate in an inactive, abortive complex. A separate subclass of Sec7-domain proteins is involved in signal transduction and possess a domain that mediates membrane binding in response to extracellular signals.
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Affiliation(s)
- C L Jackson
- Service de Biochimie et Génétique Moléculaire, CEA/Saclay, Gif-sur-Yvette, France.
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39
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Yang CZ, Mueckler M. ADP-ribosylation factor 6 (ARF6) defines two insulin-regulated secretory pathways in adipocytes. J Biol Chem 1999; 274:25297-300. [PMID: 10464254 DOI: 10.1074/jbc.274.36.25297] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ADP-ribosylation factor 6 (ARF6) appears to play an essential role in the endocytic/recycling pathway in several cell types. To determine whether ARF6 is involved in insulin-regulated exocytosis, 3T3-L1 adipocytes were infected with recombinant adenovirus expressing wild-type ARF6 or an ARF6 dominant negative mutant (D125N) that encodes a protein with nucleotide specificity modified from guanine to xanthine. Overexpression of these ARF6 proteins affected neither basal nor insulin-regulated glucose uptake in 3T3-L1 adipocytes, nor did it affect the subcellular distribution of Glut1 or Glut4. In contrast, the secretion of adipsin, a serine protease specifically expressed in adipocytes, was increased by the expression of wild-type ARF6 and was inhibited by the expression of D125N. These results indicate a requirement for ARF6 in basal and insulin-regulated adipsin secretion but not in glucose transport. Our results suggest the existence of at least two distinct pathways that undergo insulin-stimulated exocytosis in 3T3-L1 adipocytes, one for adipsin release and one for glucose transporter translocation.
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Affiliation(s)
- C Z Yang
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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40
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Gaschet J, Hsu VW. Distribution of ARF6 between membrane and cytosol is regulated by its GTPase cycle. J Biol Chem 1999; 274:20040-5. [PMID: 10391955 DOI: 10.1074/jbc.274.28.20040] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ADP-ribosylation factor (ARF) subfamily of small GTPases regulates intracellular transport. Although much is known about how ARF1 regulates transport in the secretory pathways, regulation of the endocytic pathways by ARF6 remains less understood. In particular, whereas cycling of ARF1 between membrane and cytosol represents a major mechanism of regulating its function, this regulation has been questioned for ARF6. In this study, we found that ARF6 is distributed both on membranes and in the cytosol. Cytosolic ARF6 is recruited to membranes in a GTP-dependent manner that is fundamentally similar to ARF1. However, unlike ARF1, release of membrane-bound ARF6 to the cytosol requires hydrolysis of GTP that is sensitive to the level of magnesium. These findings suggest that the GTPase cycle of ARF6 also regulates its distribution between membrane and cytosol and that this form of regulation will also likely be important for the function of ARF6. Moreover, as ARF6 has little intrinsic ability to hydrolyze GTP, magnesium concentration most likely affects the release of membrane-bound ARF6 by altering the activity of its GTPase-activating protein.
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Affiliation(s)
- J Gaschet
- Division of Rheumatology, Allergy, and Immunology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA
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41
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Millar CA, Powell KA, Hickson GR, Bader MF, Gould GW. Evidence for a role for ADP-ribosylation factor 6 in insulin-stimulated glucose transporter-4 (GLUT4) trafficking in 3T3-L1 adipocytes. J Biol Chem 1999; 274:17619-25. [PMID: 10364199 DOI: 10.1074/jbc.274.25.17619] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ADP-ribosylation factors (ARFs) play important roles in both constitutive and regulated membrane trafficking to the plasma membrane in other cells. Here we have examined their role in insulin-stimulated GLUT4 translocation in 3T3-L1 adipocytes. These cells express ARF5 and ARF6. ARF5 was identified in the soluble protein and intracellular membranes; in response to insulin some ARF5 was observed to re-locate to the plasma membrane. In contrast, ARF6 was predominantly localized to the plasma membrane and did not redistribute in response to insulin. We employed myristoylated peptides corresponding to the NH2 termini of ARF5 and ARF6 to investigate the function of these proteins. Myr-ARF6 peptide inhibited insulin-stimulated glucose transport and GLUT4 translocation by approximately 50% in permeabilized adipocytes. In contrast, myr-ARF1 and myr-ARF5 peptides were without effect. Myr-ARF5 peptide also inhibited the insulin stimulated increase in cell surface levels of GLUT1 and transferrin receptors. Myr-ARF6 peptide significantly decreased cell surface levels of these proteins in both basal and insulin-stimulated states, but did not inhibit the fold increase in response to insulin. These data suggest an important role for ARF6 in regulating cell surface levels of GLUT4 in adipocytes, and argue for a role for both ARF5 and ARF6 in the regulation of membrane trafficking to the plasma membrane.
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Affiliation(s)
- C A Millar
- Division of Biochemistry and Molecular Biology, Davidson Building, University of Glasgow, Glasgow G12 8QQ, Scotland
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42
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Venkateswarlu K, Gunn-Moore F, Tavaré JM, Cullen PJ. EGF-and NGF-stimulated translocation of cytohesin-1 to the plasma membrane of PC12 cells requires PI 3-kinase activation and a functional cytohesin-1 PH domain. J Cell Sci 1999; 112 ( Pt 12):1957-65. [PMID: 10341214 DOI: 10.1242/jcs.112.12.1957] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
ADP-ribosylation factors (ARFs) are small GTP-binding proteins that function as regulators of eukaryotic vesicle trafficking. Cytohesin-1 is a member of a family of ARF guanine nucleotide-exchange factors that contain a C-terminal pleckstrin homology (PH) domain which has been proposed to bind the lipid second messenger phosphatidylinositol 3,4,5-trisphosphate (PIP3). Here we demonstrate that in vitro, recombinant cytohesin-1 binds, via its PH domain, the inositol head group of PIP3, inositol 1,3,4, 5-tetrakisphosphate (IP4), with an affinity greater than 200-fold higher than the inositol head group of either phosphatidylinositol 4, 5-bisphosphate or phosphatidylinositol 3,4-bisphosphate. Moreover, addition of glycerol or diacetylglycerol to the 1-phosphate of IP4 does not alter the ability to interact with cytohesin-1, data which is entirely consistent with cytohesin-1 functioning as a putative PIP3 receptor. To address whether cytohesin-1 binds PIP3 in vivo, we have expressed a chimera of green fluorescent protein (GFP) fused to the N terminus of cytohesin-1 in PC12 cells. Using laser scanning confocal microscopy we demonstrate that either EGF- or NGF-stimulation of transiently transfected PC12 cells results in a rapid translocation of GFP-cytohesin-1 from the cytosol to the plasma membrane. This translocation is dependent on the cytohesin-1 PH domain and occurs with a time course that parallels the rate of plasma membrane PIP3 production. Furthermore, the translocation requires the ability of either agonist to activate PI 3-kinase, since it is inhibited by wortmannin (100 nM), LY294002 (50 microM) and by coexpression with a dominant negative p85. This data therefore suggests that in vivo cytohesin-1 can interact with PIP3 via its PH domain.
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Affiliation(s)
- K Venkateswarlu
- Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, UK
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43
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Londoño I, Marshansky V, Bourgoin S, Vinay P, Bendayan M. Expression and distribution of adenosine diphosphate-ribosylation factors in the rat kidney. Kidney Int 1999; 55:1407-16. [PMID: 10201005 DOI: 10.1046/j.1523-1755.1999.00365.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
BACKGROUND Adenosine diphosphate (ADP)-ribosylation factors (ARFs) are small guanosine triphosphatases involved in membrane traffic regulation. Aiming to explore the possible involvement of ARF1 and ARF6 in the reabsorptive properties of the nephron, we evaluated their distribution along the different renal epithelial segments. METHODS ARFs were detected by immunofluorescence and immunogold cytochemistry on renal sections, using specific anti-ARF antibodies. RESULTS ARF1 was detected in proximal and distal tubules, thick ascending limbs of Henle's loops, and cortical and medullary collecting ducts. By immunofluorescence, labeling was mostly localized to the cell cytoplasm, particularly in Golgi areas. By electron microscopy, the Golgi apparatus and the endosomal compartment of proximal and distal tubular cells were labeled. ARF6 immunofluorescence was observed in brush border membranes and the cytoplasm of proximal convoluted tubular cells, whereas it was restricted to the apical border of proximal straight tubules. ARF6 immunogold labeling was detected over microvilli and endocytic compartments of proximal tubular cells. CONCLUSIONS This study demonstrates the following: (a) the heterogeneous distributions of ARF1 and ARF6 along the nephron, (b) the existence of cytosolic and membrane-bound forms for both ARFs, and (c) their association with microvilli and endocytic compartments, suggesting an active participation in renal reabsorption.
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Affiliation(s)
- I Londoño
- Department of Pathology and Cell Biology, Université de Montréal, Quebec, Canada
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Sata M, Moss J, Vaughan M. Structural basis for the inhibitory effect of brefeldin A on guanine nucleotide-exchange proteins for ADP-ribosylation factors. Proc Natl Acad Sci U S A 1999; 96:2752-7. [PMID: 10077583 PMCID: PMC15841 DOI: 10.1073/pnas.96.6.2752] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Protein secretion through the endoplasmic reticulum and Golgi vesicular trafficking system is initiated by the binding of ADP-ribosylation factors (ARFs) to donor membranes, leading to recruitment of coatomer, bud formation, and eventual vesicle release. ARFs are approximately 20-kDa GTPases that are active with bound GTP and inactive with GDP bound. Conversion of ARF-GDP to ARF-GTP is regulated by guanine nucleotide-exchange proteins. All known ARF guanine nucleotide-exchange proteins contain a Sec7 domain of approximately 200 amino acids that includes the active site and fall into two classes that differ in molecular size and susceptibility to inhibition by the fungal metabolite brefeldin A (BFA). To determine the structural basis of BFA sensitivity, chimeric molecules were constructed by using sequences from the Sec7 domains of BFA-sensitive yeast Sec7 protein (ySec7d) and the insensitive human cytohesin-1 (C-1Sec7). Based on BFA inhibition of the activities of these molecules with recombinant yeast ARF2 as substrate, the Asp965-Met975 sequence in ySec7d was shown to be responsible for BFA sensitivity. A C-1Sec7 mutant in which Ser199, Asn204, and Pro209 were replaced with the corresponding ySec7d amino acids, Asp965, Gln970, and Met975, exhibited BFA sensitivity similar to that of recombinant ySec7d (rySec7d). Single replacement in C-1Sec7 of Ser199 or Pro209 resulted in partial inhibition by BFA, whereas replacement of Gln970 in ySec7d with Asn (as found in C-1Sec7) had no effect. As predicted, the double C-1Sec7 mutant with S199D and P209M was BFA-sensitive, demonstrating that Asp965 and Met975 in ySec7d are major molecular determinants of BFA sensitivity.
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Affiliation(s)
- M Sata
- Pulmonary-Critical Care Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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Franco M, Peters PJ, Boretto J, van Donselaar E, Neri A, D'Souza-Schorey C, Chavrier P. EFA6, a sec7 domain-containing exchange factor for ARF6, coordinates membrane recycling and actin cytoskeleton organization. EMBO J 1999; 18:1480-91. [PMID: 10075920 PMCID: PMC1171237 DOI: 10.1093/emboj/18.6.1480] [Citation(s) in RCA: 237] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have identified a human cDNA encoding a novel protein, exchange factor for ARF6 (EFA6), which contains Sec7 and pleckstrin homology domains. EFA6 promotes efficient guanine nucleotide exchange on ARF6 and is distinct from the ARNO family of ARF1 exchange factors. The protein localizes to a dense matrix on the cytoplasmic face of plasma membrane invaginations, induced on its expression. We show that EFA6 regulates endosomal membrane recycling and promotes the redistribution of transferrin receptors to the cell surface. Furthermore, expression of EFA6 induces actin-based membrane ruffles that are inhibited by co-expression of dominant-inhibitory mutant forms of ARF6 or Rac1. Our results demonstrate that by catalyzing nucleotide exchange on ARF6 at the plasma membrane and by regulating Rac1 activation, EFA6 coordinates endocytosis with cytoskeletal rearrangements.
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Affiliation(s)
- M Franco
- Centre d'Immunologie INSERM-CNRS de Marseille-Luminy, Case 906, 13288 Marseille Cedex 9, France
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Affiliation(s)
- J H Exton
- Howard Hughes Medical Institute and Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA.
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Frank SR, Hatfield JC, Casanova JE. Remodeling of the actin cytoskeleton is coordinately regulated by protein kinase C and the ADP-ribosylation factor nucleotide exchange factor ARNO. Mol Biol Cell 1998; 9:3133-46. [PMID: 9802902 PMCID: PMC25600 DOI: 10.1091/mbc.9.11.3133] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/1998] [Accepted: 09/03/1998] [Indexed: 01/31/2023] Open
Abstract
ARNO is a member of a family of guanine-nucleotide exchange factors with specificity for the ADP-ribosylation factor (ARF) GTPases. ARNO possesses a central catalytic domain with homology to yeast Sec7p and an adjacent C-terminal pleckstrin homology (PH) domain. We have previously shown that ARNO localizes to the plasma membrane in vivo and efficiently catalyzes ARF6 nucleotide exchange in vitro. In addition to a role in endocytosis, ARF6 has also been shown to regulate assembly of the actin cytoskeleton. To determine whether ARNO is an upstream regulator of ARF6 in vivo, we examined the distribution of actin in HeLa cells overexpressing ARNO. We found that, while expression of ARNO leads to disassembly of actin stress fibers, it does not result in obvious changes in cell morphology. However, treatment of ARNO transfectants with the PKC agonist phorbol 12-myristate 13-acetate results in the dramatic redistribution of ARNO, ARF6, and actin into membrane protrusions resembling lamellipodia. This process requires ARF activation, as actin rearrangement does not occur in cells expressing a catalytically inactive ARNO mutant. PKC phosphorylates ARNO at a site immediately C-terminal to its PH domain. However, mutation of this site had no effect on the ability of ARNO to regulate actin rearrangement, suggesting that phosphorylation of ARNO by PKC does not positively regulate its activity. Finally, we demonstrate that an ARNO mutant lacking the C-terminal PH domain no longer mediates cytoskeletal reorganization, indicating a role for this domain in appropriate membrane localization. Taken together, these data suggest that ARNO represents an important link between cell surface receptors, ARF6, and the actin cytoskeleton.
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Affiliation(s)
- S R Frank
- Combined Program in Pediatric Gastroenterology and Nutrition, Massachusetts General Hospital East, Charlestown, Massachusetts 02129, USA
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Zhang Q, Cox D, Tseng CC, Donaldson JG, Greenberg S. A requirement for ARF6 in Fcgamma receptor-mediated phagocytosis in macrophages. J Biol Chem 1998; 273:19977-81. [PMID: 9685333 DOI: 10.1074/jbc.273.32.19977] [Citation(s) in RCA: 163] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phagocytosis requires extension of F-actin-rich pseudopods and is accompanied by membrane fusion events. Members of the ARF family of GTPases are essential for many aspects of membrane trafficking. To test a role for this family of proteins in Fcgamma receptor-mediated phagocytosis, we utilized the fungal metabolite brefeldin A (BFA). The addition of 100 microM BFA to a subclone of RAW 264.7 macrophages disrupted the appearance and function of the Golgi apparatus as indicated by altered immunofluorescent distribution of beta-COP and reduced efflux of BODIPY C5-ceramide, a phospholipid that normally accumulates in the Golgi apparatus. In contrast, BFA had no effect on phagocytosis of IgG-coated erythrocytes. These results suggested that activation of BFA-sensitive ARFs is not required for phagocytosis. ARF6 is unique among members of the ARF family in that its membrane association is unaffected by BFA. Expression of ARF6 mutants defective in either GTP hydrolysis (Q67L) or binding (T27N) inhibited phagocytosis of IgG-coated erythrocytes and attenuated the focal accumulation of F-actin beneath the test particles. These results indicate a requirement for ARF6 in Fcgamma receptor-mediated phagocytosis and suggest that ARF6 is an important mediator of cytoskeletal alterations after Fcgamma receptor activation.
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Affiliation(s)
- Q Zhang
- Departments of Medicine and Pharmacology, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA
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Song J, Khachikian Z, Radhakrishna H, Donaldson JG. Localization of endogenous ARF6 to sites of cortical actin rearrangement and involvement of ARF6 in cell spreading. J Cell Sci 1998; 111 ( Pt 15):2257-67. [PMID: 9664047 DOI: 10.1242/jcs.111.15.2257] [Citation(s) in RCA: 139] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To study the function of the endogenous ARF6 GTP binding protein in cells, we generated an antibody which specifically recognizes ARF6, and not the other ARF proteins. Using this antibody, ARF6 was detected in all mouse organs tested and in a variety of cultured cell lines including RBL, MDCK, NRK, BHK, COS, and HeLa cells. In NRK cells, by immunofluorescence, ARF6 localized to the plasma membrane, especially at regions exhibiting membrane ruffling, and was also concentrated in a fine punctate distribution in the juxtanuclear region. This pattern of localization of the endogenous protein was similar to the localization of ARF6 when overexpressed in NRK, or HeLa, cells. Treatments which perturb cortical actin in NRK cells, such as replating of cells after trypsinization or treatment with phorbol ester, resulted in the recruitment of endogenous ARF6 to the regions of cortical actin rearrangement. ARF6 activation and subsequent membrane recycling was required for cell spreading activity since expression of the dominant-negative, GTP-binding defective mutant of ARF6, T27N, previously shown to inhibit ARF6-regulated membrane recycling, inhibited cell attachment and spreading in HeLa cells. Furthermore, phorbol ester treatment enhanced the cell spreading activities in NRK cells, and in HeLa cells, but was not observed in cells expressing T27N. Taken together, these observations support a role for endogenous ARF6 in modeling the plasma membrane and cortical actin cytoskeleton.
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Affiliation(s)
- J Song
- Laboratory of Cell Biology, NHLBI, Bld 3, Room B1-22, National Institutes of Health, Bethesda, MD 20892, USA
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