1
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Yost PP, Al-Nouman A, Curtiss J. The Rap1 small GTPase affects cell fate or survival and morphogenetic patterning during Drosophila melanogaster eye development. Differentiation 2023; 133:12-24. [PMID: 37437447 PMCID: PMC10528170 DOI: 10.1016/j.diff.2023.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 06/06/2023] [Accepted: 06/07/2023] [Indexed: 07/14/2023]
Abstract
The Drosophila melanogaster eye has been instrumental for determining both how cells communicate with one another to determine cell fate, as well as cell morphogenesis and patterning. Here, we describe the effects of the small GTPase Rap1 on the development of multiple cell types in the D. melanogaster eye. Although Rap1 has previously been linked to RTK-Ras-MAPK signaling in eye development, we demonstrate that manipulation of Rap1 activity is modified by increase or decrease of Delta/Notch signaling during several events of cell fate specification in eye development. In addition, we demonstrate that manipulating Rap1 function either in primary pigment cells or in interommatidial cells affects cone cell contact switching, primary pigment cell enwrapment of the ommatidial cluster, and sorting of secondary and tertiary pigment cells. These data suggest that Rap1 has roles in both ommatidial cell recruitment/survival and in ommatidial morphogenesis in the pupal stage. They lay groundwork for future experiments on the role of Rap1 in these events.
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Affiliation(s)
- Philip P Yost
- New Mexico State University, 1780 E University Ave, Las Cruces, NM, 88003, USA
| | | | - Jennifer Curtiss
- New Mexico State University, 1780 E University Ave, Las Cruces, NM, 88003, USA.
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2
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Wang Y, Pedigo CE, Inoue K, Tian X, Cross E, Ebenezer K, Li W, Wang Z, Shin JW, Schwartze E, Groener M, Ishibe S. Murine Epsins Play an Integral Role in Podocyte Function. J Am Soc Nephrol 2020; 31:2870-2886. [PMID: 33051360 PMCID: PMC7790213 DOI: 10.1681/asn.2020050691] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 08/30/2020] [Indexed: 01/19/2023] Open
Abstract
BACKGROUND Epsins, a family of evolutionarily conserved membrane proteins, play an essential role in endocytosis and signaling in podocytes. METHODS Podocyte-specific Epn1, Epn2, Epn3 triple-knockout mice were generated to examine downstream regulation of serum response factor (SRF) by cell division control protein 42 homolog (Cdc42). RESULTS Podocyte-specific loss of epsins resulted in increased albuminuria and foot process effacement. Primary podocytes isolated from these knockout mice exhibited abnormalities in cell adhesion and spreading, which may be attributed to reduced activation of cell division control protein Cdc42 and SRF, resulting in diminished β1 integrin expression. In addition, podocyte-specific loss of Srf resulted in severe albuminuria and foot process effacement, and defects in cell adhesion and spreading, along with decreased β1 integrin expression. CONCLUSIONS Epsins play an indispensable role in maintaining properly functioning podocytes through the regulation of Cdc42 and SRF-dependent β1 integrin expression.
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Affiliation(s)
- Ying Wang
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
- Centre for Evidence-Based Chinese Medicine, Beijing University of Chinese Medicine, Chaoyang District, Beijing, 100029, China
| | - Christopher E Pedigo
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Kazunori Inoue
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Xuefei Tian
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Elizabeth Cross
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Karen Ebenezer
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Wei Li
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Zhen Wang
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Jee Won Shin
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Eike Schwartze
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Marwin Groener
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
| | - Shuta Ishibe
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
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3
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Bhattacharjee S, Lee Y, Zhu B, Wu H, Chen Y, Chen H. Epsins in vascular development, function and disease. Cell Mol Life Sci 2020; 78:833-842. [PMID: 32930806 DOI: 10.1007/s00018-020-03642-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 08/14/2020] [Accepted: 09/03/2020] [Indexed: 12/15/2022]
Abstract
Epsins are a family of adaptor proteins involved in clathrin-dependent endocytosis. In the vasculature, epsins 1 and 2 are functionally redundant members of this family that are expressed in the endothelial cells of blood vessels and the lymphatic system throughout development and adulthood. These proteins contain a number of peptide motifs that allow them to interact with lipid moieties and a variety of proteins. These interactions facilitate the regulation of a wide range of cell signaling pathways. In this review, we focus on the involvement of epsins 1 and 2 in controlling vascular endothelial growth factor receptor signaling in angiogenesis and lymphangiogenesis. We also discuss the therapeutic implications of understanding the molecular mechanisms of epsin-mediated regulation in diseases such as atherosclerosis and diabetes.
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Affiliation(s)
- Sudarshan Bhattacharjee
- Vascular Biology Program, Harvard Medical School, Boston Children's Hospital and Department of Surgery, Boston, MA, 02115, USA
| | - Yang Lee
- Vascular Biology Program, Harvard Medical School, Boston Children's Hospital and Department of Surgery, Boston, MA, 02115, USA
| | - Bo Zhu
- Vascular Biology Program, Harvard Medical School, Boston Children's Hospital and Department of Surgery, Boston, MA, 02115, USA
| | - Hao Wu
- Vascular Biology Program, Harvard Medical School, Boston Children's Hospital and Department of Surgery, Boston, MA, 02115, USA
| | - Yabing Chen
- Department of Pathology, Birmingham Veterans Affairs Medical Center, University of Alabama at Birmingham and Research Department, Birmingham, AL, 35294, USA
| | - Hong Chen
- Vascular Biology Program, Harvard Medical School, Boston Children's Hospital and Department of Surgery, Boston, MA, 02115, USA.
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4
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Session 7: Ubiquitin & Proteasomes. Toxicol Pathol 2016. [DOI: 10.1080/01926230490882475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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5
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Eguchi K, Yoshioka Y, Yoshida H, Morishita K, Miyata S, Hiai H, Yamaguchi M. The Drosophila DOCK family protein sponge is involved in differentiation of R7 photoreceptor cells. Exp Cell Res 2013; 319:2179-95. [DOI: 10.1016/j.yexcr.2013.05.024] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2013] [Revised: 05/16/2013] [Accepted: 05/18/2013] [Indexed: 01/17/2023]
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6
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Shang F, Taylor A. Roles for the ubiquitin-proteasome pathway in protein quality control and signaling in the retina: implications in the pathogenesis of age-related macular degeneration. Mol Aspects Med 2012; 33:446-66. [PMID: 22521794 PMCID: PMC3417153 DOI: 10.1016/j.mam.2012.04.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Accepted: 04/05/2012] [Indexed: 10/28/2022]
Abstract
The accumulation of damaged or postsynthetically modified proteins and dysregulation of inflammatory responses and angiogenesis in the retina/RPE are thought be etiologically related to formation of drusen and choroidal neovascularization (CNV), hallmarks of age-related macular degeneration (AMD). The ubiquitin-proteasome pathway (UPP) plays crucial roles in protein quality control, cell cycle control and signal transduction. Selective degradation of aberrant proteins by the UPP is essential for timely removal of potentially cytotoxic damaged or otherwise abnormal proteins. Proper function of the UPP is thought to be required for cellular function. In contrast, age--or stress induced--impairment the UPP or insufficient UPP capacity may contribute to the accumulation of abnormal proteins, cytotoxicity in the retina, and AMD. Crucial roles for the UPP in eye development, regulation of signal transduction, and antioxidant responses are also established. Insufficient UPP capacity in retina and RPE can result in dysregulation of signal transduction, abnormal inflammatory responses and CNV. There are also interactions between the UPP and lysosomal proteolytic pathways (LPPs). Means that modulate the proteolytic capacity are making their way into new generation of pharmacotherapies for delaying age-related diseases and may augment the benefits of adequate nutrition, with regard to diminishing the burden of AMD.
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Affiliation(s)
- Fu Shang
- Laboratory for Nutrition and Vision Research, USDA Human Nutrition Research Center on Aging, Boston, MA 02111, USA.
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7
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Sen A, Madhivanan K, Mukherjee D, Aguilar RC. The epsin protein family: coordinators of endocytosis and signaling. Biomol Concepts 2012; 3:117-126. [PMID: 22942912 DOI: 10.1515/bmc-2011-0060] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The epsins are a conserved family of endocytic adaptors essential for cell viability in yeast and for embryo development in higher eukaryotes. Epsins function as adaptors by recognizing ubiquitinated cargo and as endocytic accessory proteins by contributing to endocytic network stability/regulation and membrane bending. Importantly, epsins play a critical role in signaling by contributing to epidermal growth factor receptor downregulation and the activation of notch and RhoGTPase pathways. In this review, we present an overview of the epsins and emphasize their functional importance as coordinators of endocytosis and signaling.
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Affiliation(s)
- Arpita Sen
- Department of Biological Sciences and Purdue Center for Cancer Research, Purdue University, West Lafayette, IN 47907, USA
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8
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Shang F, Taylor A. Role of the ubiquitin-proteasome in protein quality control and signaling: implication in the pathogenesis of eye diseases. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 109:347-96. [PMID: 22727427 DOI: 10.1016/b978-0-12-397863-9.00010-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The ubiquitin-proteasome pathway (UPP) plays important roles in many cellular functions, such as protein quality control, cell cycle control, and signal transduction. The selective degradation of aberrant proteins by the UPP is essential for the timely removal of potential cytotoxic damaged or otherwise abnormal proteins. Conversely, accumulation of the cytotoxic abnormal proteins in eye tissues is etiologically associated with many age-related eye diseases such as retina degeneration, cataract, and certain types of glaucoma. Age- or stress-induced impairment or overburdening of the UPP appears to contribute to the accumulation of abnormal proteins in eye tissues. Cell cycle and signal transduction are regulated by the conditional UPP-dependent degradation of the regulators of these processes. Impairment or overburdening of the UPP could also result in dysregulation of cell cycle control and signal transduction. The consequences of the improper cell cycle and signal transduction include defects in ocular development, wound healing, angiogenesis, or inflammatory responses. Methods that enhance or preserve UPP function or reduce its burden may be useful strategies for preventing age-related eye diseases.
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Affiliation(s)
- Fu Shang
- Laboratory for Nutrition and Vision Research, USDA Human Nutrition Research Center on Aging, Boston, Massachusetts, USA
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9
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Amerik AY, Hochstrasser M. Mechanism and function of deubiquitinating enzymes. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1695:189-207. [PMID: 15571815 DOI: 10.1016/j.bbamcr.2004.10.003] [Citation(s) in RCA: 706] [Impact Index Per Article: 37.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Attachment of ubiquitin to proteins is a crucial step in many cellular regulatory mechanisms and contributes to numerous biological processes, including embryonic development, the cell cycle, growth control, and prevention of neurodegeneration. In these diverse regulatory settings, the most widespread mechanism of ubiquitin action is probably in the context of protein degradation. Polyubiquitin attachment targets many intracellular proteins for degradation by the proteasome, and (mono)ubiquitination is often required for down-regulating plasma membrane proteins by targeting them to the vacuole (lysosome). Ubiquitin-protein conjugates are highly dynamic structures. While an array of enzymes directs the conjugation of ubiquitin to substrates, there are also dozens of deubiquitinating enzymes (DUBs) that can reverse the process. Several lines of evidence indicate that DUBs are important regulators of the ubiquitin system. These enzymes are responsible for processing inactive ubiquitin precursors, proofreading ubiquitin-protein conjugates, removing ubiquitin from cellular adducts, and keeping the 26S proteasome free of inhibitory ubiquitin chains. The present review focuses on recent discoveries that have led to a better understanding the mechanisms and physiological roles of this diverse and still poorly understood group of enzymes. We also discuss briefly some of the proteases that act on ubiquitin-like protein (UBL) conjugates and compare them to DUBs.
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Affiliation(s)
- Alexander Y Amerik
- Department of Molecular Biophysics and Biochemistry, Yale University, 266 Whitney Avenue, PO Box 208114, New Haven, CT 06520-8114, USA.
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10
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Overstreet E, Fitch E, Fischer JA. Fat facets and Liquid facets promote Delta endocytosis and Delta signaling in the signaling cells. Development 2004; 131:5355-66. [PMID: 15469967 DOI: 10.1242/dev.01434] [Citation(s) in RCA: 153] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Endocytosis modulates the Notch signaling pathway in both the signaling and receiving cells. One recent hypothesis is that endocytosis of the ligand Delta by the signaling cells is essential for Notch activation in the receiving cells. Here, we present evidence in strong support of this model. We show that in the developing Drosophila eye Fat facets (Faf), a deubiquitinating enzyme, and its substrate Liquid facets (Lqf), an endocytic epsin, promote Delta internalization and Delta signaling in the signaling cells. We demonstrate that while Lqf is necessary for three different Notch/Delta signaling events at the morphogenetic furrow, Faf is essential only for one: Delta signaling by photoreceptor precluster cells, which prevents recruitment of ectopic neurons. In addition, we show that the ubiquitin-ligase Neuralized (Neur), which ubiquitinates Delta, functions in the signaling cells with Faf and Lqf. The results presented bolster one model for Neur function in which Neur enhances Delta signaling by stimulating Delta internalization in the signaling cells. We propose that Faf plays a role similar to that of Neur in the Delta signaling cells. By deubiquitinating Lqf, which enhances the efficiency of Delta internalization, Faf stimulates Delta signaling.
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Affiliation(s)
- Erin Overstreet
- Section of Molecular Cell and Developmental Biology, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Moffett Molecular Biology Building, 2500 Speedway, Austin, TX 78712, USA
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11
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Abstract
The ubiquitin pathway (UP) is involved in regulation of many essential cellular processes usually by the degradation of regulators of these processes. For example the UP is involved in regulation of cell cycle, proliferation, differentiation, organogenesis, development, and signal transduction in the lens and retina. A functional UP has also been documented in the cornea. Upon aging or exposure to stress there is an accumulation of damaged proteins, including ubiquitinated proteins, in the lens and retina. Some of these proteins may be cytotoxic. Thus, an active UP may be required to avoid such age and disease-related accumulation of damaged proteins. In this review we will explain the biochemistry of the UP and we will document the most important studies regarding UP function in the lens, retina and cornea.
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Affiliation(s)
- Fu Shang
- Laboratory for Nutrition and Vision Research, USDA Human Nutrition Research Center on Aging, 711 Washington St, Boston MA 02111, USA.
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12
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Evans PC, Smith TS, Lai MJ, Williams MG, Burke DF, Heyninck K, Kreike MM, Beyaert R, Blundell TL, Kilshaw PJ. A novel type of deubiquitinating enzyme. J Biol Chem 2003; 278:23180-6. [PMID: 12682062 DOI: 10.1074/jbc.m301863200] [Citation(s) in RCA: 133] [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
A previous report from this laboratory described two novel proteins that have sequence similarity to A20, a negative regulator of NF-kappaB (Evans, P. C., Taylor, E. R., Coadwell, J., Heyninck, K., Beyaert, R., and Kilshaw, P. J. (2001) Biochem. J. 357, 617-623). One of these molecules, cellular zinc finger anti-NF-kappaB (Cezanne), a 100-kDa cytoplasmic protein, also suppressed NF-kappaB. Here we demonstrate that Cezanne is a novel deubiquitinating enzyme, distinct from the two known families of deubiquitinases, Types I and II. We show that Cezanne contains an N-terminal catalytic domain that belongs to the recently discovered ovarian tumor protein (OTU) superfamily, a group of proteins displaying structural similarity to cysteine proteases but having no previously described function. Recombinant Cezanne cleaved ubiquitin monomers from linear or branched synthetic ubiquitin chains and from ubiquitinated proteins. Mutation of a conserved cysteine residue in the catalytic site of the proteolytic domain caused Cezanne to co-precipitate polyubiquitinated cellular proteins. We also provide evidence for an additional ubiquitin binding site in the C-terminal part of the molecule. Our data provide the first demonstration of functional activity among OTU proteins.
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Affiliation(s)
- Paul C Evans
- Molecular Immunology Programme, The Babraham Institute, Cambridge CB2 4AT, United Kingdom.
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13
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Fischer JA. Deubiquitinating enzymes: their roles in development, differentiation, and disease. INTERNATIONAL REVIEW OF CYTOLOGY 2003; 229:43-72. [PMID: 14669954 DOI: 10.1016/s0074-7696(03)29002-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The ubiquitin-mediated proteolysis pathway has come a long way in the past decade. At first thought to be an unglamorous garbage dump for damaged proteins, the ubiquitin pathway has been shown to regulate virtually everything that occurs in the cell. Deubiquitinating enzymes, which cleave ubiquitin-protein bonds, are the largest group of enzymes in the pathway, yet they are the least well understood. Deubiquitinating enzymes have two kinds of functions: housekeeping and regulatory. The housekeeping enzymes facilitate the proteolytic pathway. By contrast, the regulatory enzymes control the ubiquitination of specific protein substrates; their relationship to ubiquitination is analgous to that of phosphatases with respect to phosphorylation. Here, I review the current state of knowledge of the deubiquitinating enzymes. I focus particularly on the known regulatory enzymes, and also on the housekeeping enzymes that are implicated in development of disease.
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Affiliation(s)
- Janice A Fischer
- Section of Molecular Cell and Developmental Biology, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
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14
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Chen X, Zhang B, Fischer JA. A specific protein substrate for a deubiquitinating enzyme: Liquid facets is the substrate of Fat facets. Genes Dev 2002; 16:289-94. [PMID: 11825870 PMCID: PMC155328 DOI: 10.1101/gad.961502] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Eukaryotic genomes encode large families of deubiquitinating enzymes (DUBs). Genetic data suggest that Fat facets (Faf), a Drosophila DUB essential for patterning the compound eye, might have a novel regulatory function; Faf might reverse the ubiquitination of a specific substrate, thereby preventing proteasomal degradation of that protein. Additional genetic data implicate Liquid facets (Lqf), a homolog of the vertebrate endocytic protein epsin, as a candidate for the key substrate of Faf. Here, biochemical experiments critical to testing this model were performed. The results show definitively that Lqf is the key substrate of Faf in the eye; Lqf concentration is Faf-dependent, Lqf is ubiquitinated in vivo and deubiquitinated by Faf, and Lqf and Faf interact physically.
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Affiliation(s)
- Xin Chen
- Section of Molecular Cell and Developmental Biology, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
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15
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Fischer JA. Developmental regulation through protein stability. Results Probl Cell Differ 2002; 37:151-167. [PMID: 25707074 DOI: 10.1007/978-3-540-45398-7_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Affiliation(s)
- Janice A Fischer
- The University of Texas at Austin, Section of Molecular Cell and Developmental Biology, The Institute for Cellular and Molecular Biology, Moffett Molecular Biology Building, 2500 Speedway, Austin, Texas 78712, USA
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16
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Pantaleon M, Kanai-Azuma M, Mattick JS, Kaibuchi K, Kaye PL, Wood SA. FAM deubiquitylating enzyme is essential for preimplantation mouse embryo development. Mech Dev 2001; 109:151-60. [PMID: 11731229 DOI: 10.1016/s0925-4773(01)00551-2] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
FAM is a developmentally regulated substrate-specific deubiquitylating enzyme. It binds the cell adhesion and signalling molecules beta-catenin and AF-6 in vitro, and stabilises both in mammalian cell culture. To determine if FAM is required at the earliest stages of mouse development we examined its expression and function in preimplantation mouse embryos. FAM is expressed at all stages of preimplantation development from ovulation to implantation. Exposure of two-cell embryos to FAM-specific antisense, but not sense, oligodeoxynucleotides resulted in depletion of the FAM protein and failure of the embryos to develop to blastocysts. Loss of FAM had two physiological effects, namely, a decrease in cleavage rate and an inhibition of cell adhesive events. Depletion of FAM protein was mirrored by a loss of beta-catenin such that very little of either protein remained following 72h culture. The residual beta-catenin was localised to sites of cell-cell contact suggesting that the cytoplasmic pool of beta-catenin is stabilised by FAM. Although AF-6 levels initially decreased they returned to normal. However, the nascent protein was mislocalised at the apical surface of blastomeres. Therefore FAM is required for preimplantation mouse embryo development and regulates beta-catenin and AF-6 in vivo.
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Affiliation(s)
- M Pantaleon
- Department of Physiology and Pharmacology, The University of Queensland, Queensland 4072, Brisbane, Australia
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17
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Abstract
Cellular genes that are mutated in neurodegenerative diseases code for proteins that are expressed throughout neural development. Genetic analysis suggests that these genes are essential for a broad range of normal neurodevelopmental processes. The proteins they code for interact with numerous other cellular proteins that are components of signaling pathways involved in patterning of the neural tube and in regional specification of neuronal subtypes. Further, pathogenetic mutations of these genes can cause progressive, sublethal alterations in the cellular homeostasis of evolving regional neuronal subpopulations, culminating in late-onset cell death. Therefore, as a consequence of the disease mutations, targeted cell populations may retain molecular traces of abnormal interactions with disease-associated proteins by exhibiting changes in a spectrum of normal cellular functions and enhanced vulnerability to a host of environmental stressors. These observations suggest that the normal functions of these disease-associated proteins are to ensure the fidelity and integration of developmental events associated with the progressive elaboration of neuronal subtypes as well as the maintenance of mature neuronal populations during adult life. The ability to identify alterations within vulnerable neuronal precursors present in pre-symptomatic individuals prior to the onset of irrevocable cellular injury may help foster the development of effective therapeutic interventions using evolving pharmacologic, gene and stem cell technologies.
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Affiliation(s)
- M F Mehler
- Laboratory of Developmental and Molecular Neuroscience, Department of Neurology, Rose F. Kennedy Center for Research in Mental Retardation and Developmental Disabilities, Albert Einstein College of Medicine, Bronx 10461, NY, USA.
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18
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Chen X, Li Q, Fischer JA. Genetic analysis of the Drosophila DNAprim gene. The function of the 60-kd primase subunit of DNA polymerase opposes the fat facets signaling pathway in the developing eye. Genetics 2000; 156:1787-95. [PMID: 11102374 PMCID: PMC1461376 DOI: 10.1093/genetics/156.4.1787] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The Drosophila DNAprim gene encodes the large subunit (60 kD) of DNA primase, the part of DNA polymerase alpha that synthesizes RNA primers during DNA replication. The precise function of the 60-kD subunit is unknown. In a mutagenesis screen for suppressors of the fat facets (faf) mutant eye phenotype, we identified mutations in DNAprim. The faf gene encodes a deubiquitinating enzyme required specifically for patterning the compound eye. The DNA sequences of four DNAprim alleles were determined and these define essential protein domains. We show that while flies lacking DNAprim activity are lethal, flies with reduced DNAprim activity display morphological defects in their eyes, and unlike faf mutants, cell cycle abnormalities in larval eye discs. Mechanisms by which DNA primase levels might influence the faf-dependent cell communication pathway are discussed.
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Affiliation(s)
- X Chen
- Section of Molecular Cell and Developmental Biology, Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas 78712, USA
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19
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Cadavid AL, Ginzel A, Fischer JA. The function of the Drosophila fat facets deubiquitinating enzyme in limiting photoreceptor cell number is intimately associated with endocytosis. Development 2000; 127:1727-36. [PMID: 10725248 DOI: 10.1242/dev.127.8.1727] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Fat facets is a deubiquitinating enzyme required in a cell communication pathway that limits to eight the number of photoreceptor cells in each facet of the Drososphila compound eye. Genetic data support a model whereby Faf removes ubiquitin, a polypeptide tag for protein degradation, from a specific ubiquitinated protein thus preventing its degradation. Here, mutations in the liquid facets gene were identified as dominant enhancers of the fat facets mutant eye phenotype. The liquid facets locus encodes epsin, a vertebrate protein associated with the clathrin endocytosis complex. The results of genetic experiments reveal that fat facets and liquid facets facilitate endocytosis and function in common cells to generate an inhibitory signal that prevents ectopic photoreceptor determination. Moreover, it is demonstrated that the fat facets mutant phenotype is extraordinarily sensitive to the level of liquid facets expression. We propose that Liquid facets is a candidate for the critical substrate of Fat facets in the eye.
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Affiliation(s)
- A L Cadavid
- Section of Molecular Cell and Developmental Biology, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712 USA
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20
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Kanai-Azuma M, Mattick JS, Kaibuchi K, Wood SA. Co-localization of FAM and AF-6, the mammalian homologues of Drosophila faf and canoe, in mouse eye development. Mech Dev 2000; 91:383-6. [PMID: 10704870 DOI: 10.1016/s0925-4773(99)00294-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The Drosophila fat facets and canoe genes regulate non-neural cell fate decisions during ommatidium formation. We have shown previously that the FAM (fat facets in mouse) de-ubiquitinating enzyme regulates the function of AF-6, (mammalian canoe homologue), in the MDCK epithelial cell line (Taya et al., 1998. The Ras target AF-6 is a substrate of the fam de-ubiquitinating enzyme. J. Cell Biol. 142, 1053-1062). We report here that the expression of the FAM and AF-6 proteins overlaps extensively in the mouse eye from embryogenesis to maturity, especially in the non-neural epithelia including the retinal pigment epithelium, subcapsular epithelium of the lens and corneal epithelium. Expression is not limited to the epithelia however, as FAM and AF-6 also co-localize during lens fibre development as well as in sub-populations of the neural retina.
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Affiliation(s)
- M Kanai-Azuma
- Centre for Molecular and Cellular Biology, The University of Queensland, Brisbane, QLD, Australia
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Wu Z, Li Q, Fortini ME, Fischer JA. Genetic analysis of the role of the drosophila fat facets gene in the ubiquitin pathway. DEVELOPMENTAL GENETICS 1999; 25:312-20. [PMID: 10570463 DOI: 10.1002/(sici)1520-6408(1999)25:4<312::aid-dvg5>3.0.co;2-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The Drosophila fat facets gene encodes a deubiquitinating enzyme required during eye development to limit the number of photoreceptors in each facet to eight. Ubiquitin is a small polypeptide that targets proteins for degradation by the proteasome. Deubiquitinating enzymes cleave ubiquitin-protein bonds. In order to investigate the role of FAT FACETS in the ubiquitin pathway, genetic interactions between fat facets and the Drosophila UbcD1 gene were assessed. In addition, three yeast deubiquitinating enzyme genes were tested for their ability to substitute for fat facets in the developing Drosophila eye and for their effects on eye morphology. The results of these experiments support the hypothesis that FAT FACETS activity antagonizes that of the proteolytic machinery. The implications of these results for the specificity of FAF and yeast UBPs are discussed as well.
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Affiliation(s)
- Z Wu
- Department of Molecular Cell and Developmental Biology and Institute for Cellular and Molecular Biology, University of Texas at Austin, 78712, USA
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Mykles DL. Intracellular proteinases of invertebrates: calcium-dependent and proteasome/ubiquitin-dependent systems. INTERNATIONAL REVIEW OF CYTOLOGY 1998; 184:157-289. [PMID: 9697313 DOI: 10.1016/s0074-7696(08)62181-6] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Cytosolic proteinases carry out a variety of regulatory functions by controlling protein levels and/or activities within cells. Calcium-dependent and ubiquitin/proteasome-dependent pathways are common to all eukaryotes. The former pathway consists of a diverse group of Ca(2+)-dependent cysteine proteinases (CDPs; calpains in vertebrate tissues). The latter pathway is highly conserved and consists of ubiquitin, ubiquitin-conjugating enzymes, deubiquitinases, and the proteasome. This review summarizes the biochemical properties and genetics of invertebrate CDPs and proteasomes and their roles in programmed cell death, stress responses (heat shock and anoxia), skeletal muscle atrophy, gametogenesis and fertilization, development and pattern formation, cell-cell recognition, signal transduction and learning, and photoreceptor light adaptation. These pathways carry out bulk protein degradation in the programmed death of the intersegmental and flight muscles of insects and of individuals in a colonial ascidian; molt-induced atrophy of crustacean claw muscle; and responses of brine shrimp, mussels, and insects to environmental stress. Selective proteolysis occurs in response to specific signals, such as in modulating protein kinase A activity in sea hare and fruit fly associated with learning; gametogenesis, differentiation, and development in sponge, echinoderms, nematode, ascidian, and insects; and in light adaptation of photoreceptors in the eyes of squid, insects, and crustaceans. Proteolytic activities and specificities are regulated through proteinase gene expression (CDP isozymes and proteasomal subunits), allosteric regulators, and posttranslational modifications, as well as through specific targeting of protein substrates by a diverse assemblage of ubiquitin-conjugases and deubiquitinases. Thus, the regulation of intracellular proteolysis approaches the complexity and versatility of transcriptional and translational mechanisms.
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Affiliation(s)
- D L Mykles
- Department of Biology, Colorado State University, Fort Collins 80523, USA
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Li Q, Hariharan IK, Chen F, Huang Y, Fischer JA. Genetic interactions with Rap1 and Ras1 reveal a second function for the fat facets deubiquitinating enzyme in Drosophila eye development. Proc Natl Acad Sci U S A 1997; 94:12515-20. [PMID: 9356481 PMCID: PMC25022 DOI: 10.1073/pnas.94.23.12515] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The Drosophila fat facets gene encodes a deubiquitinating enzyme that regulates a cell communication pathway essential very early in eye development, prior to facet assembly, to limit the number of photoreceptor cells in each facet of the compound eye to eight. The Fat facets protein facilitates the production of a signal in cells outside the developing facets that inhibits neural development of particular facet precursor cells. Novel gain-of-function mutations in the Drosophila Rap1 and Ras1 genes are described herein that interact genetically with fat facets mutations. Analysis of these genetic interactions reveals that Fat facets has an additional function later in eye development involving Rap1 and Ras1 proteins. Moreover, the results suggest that undifferentiated cells outside the facet continue to influence facet assembly later in eye development.
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Affiliation(s)
- Q Li
- Department of Zoology, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
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