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Putar D, Čizmar A, Chao X, Šimić M, Šoštar M, Ćutić T, Mijanović L, Smolko A, Tu H, Cosson P, Weber I, Cai H, Filić V. IqgC is a potent regulator of macropinocytosis in the presence of NF1 and its loading to macropinosomes is dependent on RasG. Open Biol 2024; 14:230372. [PMID: 38263885 PMCID: PMC10806400 DOI: 10.1098/rsob.230372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 11/26/2023] [Indexed: 01/25/2024] Open
Abstract
RasG is a major regulator of macropinocytosis in Dictyostelium discoideum. Its activity is under the control of an IQGAP-related protein, IqgC, which acts as a RasG-specific GAP (GTPase activating protein). IqgC colocalizes with the active Ras at the macropinosome membrane during its formation and for some time after the cup closure. However, the loss of IqgC induces only a minor enhancement of fluid uptake in axenic cells that already lack another RasGAP, NF1. Here, we show that IqgC plays an important role in the regulation of macropinocytosis in the presence of NF1 by restricting the size of macropinosomes. We further provide evidence that interaction with RasG is indispensable for the recruitment of IqgC to forming macropinocytic cups. We also demonstrate that IqgC interacts with another small GTPase from the Ras superfamily, Rab5A, but is not a GAP for Rab5A. Since mammalian Rab5 plays a key role in early endosome maturation, we hypothesized that IqgC could be involved in macropinosome maturation via its interaction with Rab5A. Although an excessive amount of Rab5A reduces the RasGAP activity of IqgC in vitro and correlates with IqgC dissociation from endosomes in vivo, the physiological significance of the Rab5A-IqgC interaction remains elusive.
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Affiliation(s)
- Darija Putar
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Anja Čizmar
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Xiaoting Chao
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101 Beijing, People's Republic of China
- College of Life Sciences, University of Chinese Academy of Sciences, 100049 Beijing, People's Republic of China
| | - Marija Šimić
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Marko Šoštar
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Tamara Ćutić
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Lucija Mijanović
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Ana Smolko
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Hui Tu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101 Beijing, People's Republic of China
- College of Life Sciences, University of Chinese Academy of Sciences, 100049 Beijing, People's Republic of China
| | - Pierre Cosson
- Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Igor Weber
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
| | - Huaqing Cai
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101 Beijing, People's Republic of China
- College of Life Sciences, University of Chinese Academy of Sciences, 100049 Beijing, People's Republic of China
| | - Vedrana Filić
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
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Jagić M, Vuk T, Škiljaica A, Markulin L, Vičić Bočkor V, Tokić M, Miškec K, Razdorov G, Habazin S, Šoštar M, Weber I, Bauer N, Leljak Levanić D. BPM1 regulates RdDM-mediated DNA methylation via a cullin 3 independent mechanism. Plant Cell Rep 2022; 41:2139-2157. [PMID: 36066603 DOI: 10.1007/s00299-022-02911-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 07/26/2022] [Indexed: 06/15/2023]
Abstract
BPM1 interacts with components of the DDR complex and stimulates DNA methylation at CHH sites, suggesting its involvement in the RdDM methylation pathway. The best-known function of MATH-BTB proteins, including Arabidopsis BPM proteins, is their role as substrate-specific adaptors of CUL3-based E3 ligases in the ubiquitin-proteasome pathway. This paper reports a new CUL3-independent role of BPM1 in RNA-directed DNA methylation (RdDM). Using quantitative and qualitative Y2H, pull down, microscale thermophoresis and FRET-FLIM, we demonstrate that BPM1 interacts with DMS3 and RDM1, components of the chromatin remodeling DDR complex involved in the recruitment of the RdDM methylation machinery. All three proteins colocalized predominantly in the nucleus. The MATH domain, which specifically binds proteins destined for degradation, was not essential for interactions with DMS3 and RDM1. In plants overexpressing BPM1, endogenous DMS3 protein levels were stable, indicating that BPM1 does not induce proteasomal degradation. In RDM1-overexpressing plants, RDM1 was not ubiquitinated. Together, these results suggest that BPM1 does not mediate the degradation of DMS3 and RDM1. Additionally, overexpression of BPM1 caused increased global methylation levels as well as CHH methylation in promoters of two RdDM-regulated genes, FWA and CML41. Overall, BPM1 seems to have a stimulating effect on RdDM activity, and this role appears to be unrelated to its known function as a Cul3-based E3 ligase adaptor.
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Affiliation(s)
- Mateja Jagić
- Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, Zagreb, Croatia
| | - Tamara Vuk
- Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, Zagreb, Croatia
| | - Andreja Škiljaica
- Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, Zagreb, Croatia
| | - Lucija Markulin
- Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, Zagreb, Croatia
| | - Vedrana Vičić Bočkor
- Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, Zagreb, Croatia
| | - Mirta Tokić
- Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, Zagreb, Croatia
| | - Karlo Miškec
- Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, Zagreb, Croatia
| | | | | | - Marko Šoštar
- Division of Molecular Biology, Institute Ruđer Bošković, Zagreb, Croatia
| | - Igor Weber
- Division of Molecular Biology, Institute Ruđer Bošković, Zagreb, Croatia
| | - Nataša Bauer
- Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, Zagreb, Croatia
| | - Dunja Leljak Levanić
- Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, Zagreb, Croatia.
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Radić M, Šoštar M, Weber I, Ćetković H, Slade N, Herak Bosnar M. The Subcellular Localization and Oligomerization Preferences of NME1/NME2 upon Radiation-Induced DNA Damage. Int J Mol Sci 2020; 21:ijms21072363. [PMID: 32235358 PMCID: PMC7177722 DOI: 10.3390/ijms21072363] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 03/20/2020] [Accepted: 03/26/2020] [Indexed: 02/06/2023] Open
Abstract
Nucleoside diphosphate kinases (NDPK/NME/Nm23) are enzymes composed of subunits NME1/NDPK A and NME2/NDPK B, responsible for the maintenance of the cellular (d)NTP pool and involved in other cellular processes, such as metastasis suppression and DNA damage repair. Although eukaryotic NDPKs are active only as hexamers, it is unclear whether other NME functions require the hexameric form, and how the isoenzyme composition varies in different cellular compartments. To examine the effect of DNA damage on intracellular localization of NME1 and NME2 and the composition of NME oligomers in the nucleus and the cytoplasm, we used live-cell imaging and the FRET/FLIM technique. We showed that exogenous NME1 and NME2 proteins co-localize in the cytoplasm of non-irradiated cells, and move simultaneously to the nucleus after gamma irradiation. The FRET/FLIM experiments imply that, after DNA damage, there is a slight shift in the homomer/heteromer balance between the nucleus and the cytoplasm. Collectively, our results indicate that, after irradiation, NME1 and NME2 engage in mutual functions in the nucleus, possibly performing specific functions in their homomeric states. Finally, we demonstrated that fluorophores fused to the N-termini of NME polypeptides produce the largest FRET effect and thus recommend this orientation for use in similar studies.
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Affiliation(s)
- Martina Radić
- Division of Molecular Medicine, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia; (M.R.); (N.S.)
| | - Marko Šoštar
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia; (M.Š.); (I.W.); (H.Ć.)
| | - Igor Weber
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia; (M.Š.); (I.W.); (H.Ć.)
| | - Helena Ćetković
- Division of Molecular Biology, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia; (M.Š.); (I.W.); (H.Ć.)
| | - Neda Slade
- Division of Molecular Medicine, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia; (M.R.); (N.S.)
| | - Maja Herak Bosnar
- Division of Molecular Medicine, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia; (M.R.); (N.S.)
- Correspondence: ; Tel.: +385-1-456-0996
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Filić V, Marinović M, Šoštar M, Weber I. Modulation of small GTPase activity by NME proteins. J Transl Med 2018; 98:589-601. [PMID: 29434248 DOI: 10.1038/s41374-018-0023-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2017] [Revised: 12/06/2017] [Accepted: 12/29/2017] [Indexed: 12/26/2022] Open
Abstract
NME proteins are reported to influence signal transduction activity of small GTPases from the Ras superfamily by diverse mechanisms in addition to their generic NDP kinase activity, which replenishes the cytoplasmic pool of GTP. Comprehensive evidence shows that NME proteins modulate the activity of Ras GTPases, in particular members of the Rho family, via binding to their major activators GEFs. Direct interaction between several NMEs and Ras GTPases were also indicated in vitro and in vivo. These modes of regulation are mainly independent of the NME's kinase activity. NMEs also modulate the Ras-mediated signal transduction by interfering with the formation of a Ras signaling complex at the plasma membrane. In several examples, NMEs were proposed to perform the role of GAP proteins by promoting hydrolysis of the bound GTP, but this activity still requires additional verification. Early suggestions that NMEs can activate small GTPases by direct phosphorylation of the bound GDP, or by high-rate loading of GTP onto a closely apposed GTPase, were largely dismissed. In this review article, we survey and put into perspective published examples of identified and hypothetical mechanisms of Ras signaling modulation by NME proteins. We also point out involvement of NMEs in the transcriptional regulation of components of Ras GTPases-mediated signal transduction pathways, and reciprocal regulation of NME function by small GTPases, particularly related to NME's binding to membranes.
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Affiliation(s)
- Vedrana Filić
- Ruđer Bošković Institute, Division of Molecular Biology, Bijenička 54, HR-10000, Zagreb, Croatia
| | - Maja Marinović
- Ruđer Bošković Institute, Division of Molecular Biology, Bijenička 54, HR-10000, Zagreb, Croatia
| | - Marko Šoštar
- Ruđer Bošković Institute, Division of Molecular Biology, Bijenička 54, HR-10000, Zagreb, Croatia
| | - Igor Weber
- Ruđer Bošković Institute, Division of Molecular Biology, Bijenička 54, HR-10000, Zagreb, Croatia.
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Marinović M, Šoštar M, Filić V, Antolović V, Weber I. Quantitative imaging of Rac1 activity in Dictyostelium cells with a fluorescently labelled GTPase-binding domain from DPAKa kinase. Histochem Cell Biol 2016; 146:267-79. [DOI: 10.1007/s00418-016-1440-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/19/2016] [Indexed: 02/06/2023]
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