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Taylor KL, Taylor RJ, Richters KE, Huynh B, Carrington J, McDermott ME, Wilson RL, Dent EW. Opposing functions of F-BAR proteins in neuronal membrane protrusion, tubule formation, and neurite outgrowth. Life Sci Alliance 2019; 2:2/3/e201800288. [PMID: 31160379 PMCID: PMC6549137 DOI: 10.26508/lsa.201800288] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 05/15/2019] [Accepted: 05/17/2019] [Indexed: 01/08/2023] Open
Abstract
Neurite formation is a fundamental antecedent to axon and dendrite formation, but the mechanisms that underlie this important process are poorly characterized. Here, we demonstrate that two F-BAR proteins, CIP4 and FBP17, have opposing functions in early cortical neuron development. The F-BAR family of proteins play important roles in many cellular processes by regulating both membrane and actin dynamics. The CIP4 family of F-BAR proteins is widely recognized to function in endocytosis by elongating endocytosing vesicles. However, in primary cortical neurons, CIP4 concentrates at the tips of extending lamellipodia and filopodia and inhibits neurite outgrowth. Here, we report that the highly homologous CIP4 family member, FBP17, induces tubular structures in primary cortical neurons and results in precocious neurite formation. Through domain swapping and deletion experiments, we demonstrate that a novel polybasic region between the F-BAR and HR1 domains is required for membrane bending. Moreover, the presence of a poly-PxxP region in longer splice isoforms of CIP4 and FBP17 largely reverses the localization and function of these proteins. Thus, CIP4 and FBP17 function as an antagonistic pair to fine-tune membrane protrusion, endocytosis, and neurite formation during early neuronal development.
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Affiliation(s)
- Kendra L Taylor
- University of Wisconsin-Madison, Neuroscience Training Program, Madison, WI, USA
| | - Russell J Taylor
- University of Wisconsin-Madison, Neuroscience Training Program, Madison, WI, USA
| | - Karl E Richters
- University of Wisconsin-Madison, Department of Neuroscience, Madison, WI, USA
| | - Brandon Huynh
- University of Wisconsin-Madison, Department of Neuroscience, Madison, WI, USA
| | - Justin Carrington
- University of Wisconsin-Madison, Department of Neuroscience, Madison, WI, USA
| | - Maeve E McDermott
- University of Wisconsin-Madison, Department of Neuroscience, Madison, WI, USA
| | - Rebecca L Wilson
- University of Wisconsin-Madison, Department of Neuroscience, Madison, WI, USA
| | - Erik W Dent
- University of Wisconsin-Madison, Department of Neuroscience, Madison, WI, USA
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2
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Blue RE, Curry EG, Engels NM, Lee EY, Giudice J. How alternative splicing affects membrane-trafficking dynamics. J Cell Sci 2018; 131:jcs216465. [PMID: 29769303 PMCID: PMC6031328 DOI: 10.1242/jcs.216465] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The cell biology field has outstanding working knowledge of the fundamentals of membrane-trafficking pathways, which are of critical importance in health and disease. Current challenges include understanding how trafficking pathways are fine-tuned for specialized tissue functions in vivo and during development. In parallel, the ENCODE project and numerous genetic studies have revealed that alternative splicing regulates gene expression in tissues and throughout development at a post-transcriptional level. This Review summarizes recent discoveries demonstrating that alternative splicing affects tissue specialization and membrane-trafficking proteins during development, and examines how this regulation is altered in human disease. We first discuss how alternative splicing of clathrin, SNAREs and BAR-domain proteins influences endocytosis, secretion and membrane dynamics, respectively. We then focus on the role of RNA-binding proteins in the regulation of splicing of membrane-trafficking proteins in health and disease. Overall, our aim is to comprehensively summarize how trafficking is molecularly influenced by alternative splicing and identify future directions centered on its physiological relevance.
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Affiliation(s)
- R Eric Blue
- Department of Cell Biology & Physiology, School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Ennessa G Curry
- Department of Cell Biology & Physiology, School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Nichlas M Engels
- Department of Cell Biology & Physiology, School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Eunice Y Lee
- Department of Cell Biology & Physiology, School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jimena Giudice
- Department of Cell Biology & Physiology, School of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- McAllister Heart Institute, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Curriculum in Genetics and Molecular Biology (GMB), The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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3
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CIP4 is required for the hypertrophic growth of neonatal cardiac myocytes. J Biomed Sci 2013; 20:56. [PMID: 23915320 PMCID: PMC3750294 DOI: 10.1186/1423-0127-20-56] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 08/01/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND CIP4 is a scaffold protein that regulates membrane deformation and tubulation, organization of the actin cytoskeleton, endocytosis of growth factor receptors, and vesicle trafficking. Although expressed in the heart, CIP4 has not been studied with regards to its potential function in cardiac myocytes. RESULTS We now show using RNA interference that CIP4 expression in neonatal rat ventricular myocytes is required for the induction of non-mitotic, hypertrophic growth by the α-adrenergic agonist phenylephrine, the IL-6 cytokine leukemia inhibitor factor, and fetal bovine serum, as assayed using morphometry, immunocytochemistry for the hypertrophic marker atrial natriuretic factor and [3H]leucine incorporation for de novo protein synthesis. This requirement was consistent with the induction of CIP4 expression by hypertrophic stimulation. The inhibition of myocyte hypertrophy by CIP4 small interfering oligonucleotides (siRNA) was rescued by expression of a recombinant CIP4 protein, but not by a mutant lacking the N-terminal FCH domain responsible for CIP4 intracellular localization. CONCLUSIONS These results imply that CIP4 plays a significant role in the intracellular hypertrophic signal transduction network that controls the growth of cardiac myocytes in heart disease.
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Pichot CS, Arvanitis C, Hartig SM, Jensen SA, Bechill J, Marzouk S, Yu J, Frost JA, Corey SJ. Cdc42-interacting protein 4 promotes breast cancer cell invasion and formation of invadopodia through activation of N-WASp. Cancer Res 2010; 70:8347-56. [PMID: 20940394 DOI: 10.1158/0008-5472.can-09-4149] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In the earliest stages of metastasis, breast cancer cells must reorganize the cytoskeleton to affect cell shape change and promote cell invasion and motility. These events require the cytoskeletal regulators Cdc42 and Rho, their effectors such as N-WASp/WAVE, and direct inducers of actin polymerization such as Arp2/3. Little consideration has been given to molecules that shape the cell membrane. The F-BAR proteins CIP4, TOCA-1, and FBP17 generate membrane curvature and act as scaffolding proteins for activated Cdc42 and N-WASp. We found that expression of CIP4, but not TOCA-1 or FBP17, was increased in invasive breast cancer cell lines in comparison with weakly or noninvasive breast cancer cell lines. Endogenous CIP4 localized to the leading edge of migrating cells and to invadopodia in cells invading gelatin. Because CIP4 serves as a scaffolding protein for Cdc42, Src, and N-WASp, we tested whether loss of CIP4 could result in decreased N-WASp function. Interaction between CIP4 and N-WASp was epidermal growth factor responsive, and CIP4 silencing by small interfering RNA caused decreased tyrosine phosphorylation of N-WASp at a Src-dependent activation site (Y256). CIP4 silencing also impaired the migration and invasion of MDA-MB-231 cells and was associated with decreased formation of invadopodia and gelatin degradation. This study presents a new role for CIP4 in the promotion of migration and invasion of MDA-MB-231 breast cancer cells and establishes the contribution of F-BAR proteins to cancer cell motility and invasion.
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Affiliation(s)
- Christina S Pichot
- Integrative Biology and Pharmacology, University of Texas Health Science Center, Baylor College of Medicine, Houston, Texas, USA
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5
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Feng Y, Hartig SM, Bechill JE, Blanchard EG, Caudell E, Corey SJ. The Cdc42-interacting protein-4 (CIP4) gene knock-out mouse reveals delayed and decreased endocytosis. J Biol Chem 2010; 285:4348-54. [PMID: 19920150 PMCID: PMC2836039 DOI: 10.1074/jbc.m109.041038] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Revised: 11/06/2009] [Indexed: 12/22/2022] Open
Abstract
The newly described F-BAR (Fer/CIP4 and Bin, amphiphysin, Rvs) family of proteins includes Cdc42-interacting protein-4 (CIP4), formin-binding protein-17 (FBP-17) and transactivator of cytoskeletal assembly-1 (Toca-1), and drives membrane deformation and invagination. Membrane remodeling affects endocytosis, vesicle budding, and cargo selection. The F-BAR family presents a novel family of proteins, which little is known about their in vivo function. We investigated the physiological role of CIP4, by creating Cip4-null mice through homologous recombination. Compared with their wild-type littermates, the Cip4-null mice displayed lower early post-prandial glucose levels. Adipocytes isolated from Cip4-null mice exhibited increased [(14)C]2-deoxyglucose uptake compared with cells from wild-type mice. The enhanced insulin sensitivity was not due to higher levels of insulin or phospho-Akt, a critical player in insulin signaling. However, higher glucose transporter 4 (GLUT4) levels were detected in muscle membrane fractions in Cip4-null mice under insulin stimulation. Mouse embryonic fibroblasts from Cip4-null mice demonstrated decreased transferrin uptake, fluorescein isothiocyanate-dextran, and horseradish peroxidase uptake, indicating that CIP4 affects multiple modes of endocytosis. These studies demonstrate a physiological role for CIP4 in endocytosis leading to a whole animal phenotype.
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Affiliation(s)
- Yanming Feng
- From the Division of Pediatrics, University of Texas, MD Anderson Cancer Center, Houston, Texas 77030
- the Departments of Pediatrics and Cellular and Molecular Biology and the Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, Illinois 60611, and
| | - Sean M. Hartig
- From the Division of Pediatrics, University of Texas, MD Anderson Cancer Center, Houston, Texas 77030
- the Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030
| | - John E. Bechill
- the Departments of Pediatrics and Cellular and Molecular Biology and the Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, Illinois 60611, and
| | - Elisabeth G. Blanchard
- From the Division of Pediatrics, University of Texas, MD Anderson Cancer Center, Houston, Texas 77030
| | - Eva Caudell
- From the Division of Pediatrics, University of Texas, MD Anderson Cancer Center, Houston, Texas 77030
| | - Seth J. Corey
- From the Division of Pediatrics, University of Texas, MD Anderson Cancer Center, Houston, Texas 77030
- the Departments of Pediatrics and Cellular and Molecular Biology and the Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, Illinois 60611, and
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6
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Hartig SM, Ishikura S, Hicklen RS, Feng Y, Blanchard EG, Voelker KA, Pichot CS, Grange RW, Raphael RM, Klip A, Corey SJ. The F-BAR protein CIP4 promotes GLUT4 endocytosis through bidirectional interactions with N-WASp and Dynamin-2. J Cell Sci 2009; 122:2283-91. [PMID: 19509061 DOI: 10.1242/jcs.041343] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
F-BAR proteins are a newly described family of proteins with unknown physiological significance. Because F-BAR proteins, including Cdc42 interacting protein-4 (CIP4), drive membrane deformation and affect endocytosis, we investigated the role of CIP4 in GLUT4 traffic by flow cytometry in GLUT4myc-expressing L6 myoblasts (L6 GLUT4myc). L6 GLUT4myc cells express CIP4a as the predominant F-BAR protein. siRNA knockdown of CIP4 increased insulin-stimulated (14)C-deoxyglucose uptake by elevating cell-surface GLUT4. Enhanced surface GLUT4 was due to decreased endocytosis, which correlated with lower transferrin internalization. Immunoprecipitation of endogenous CIP4 revealed that CIP4 interacted with N-WASp and Dynamin-2 in an insulin-dependent manner. FRET confirmed the insulin-dependent, subcellular properties of these interactions. Insulin exposure stimulated specific interactions in plasma membrane and cytosolic compartments, followed by a steady-state response that underlies the coordination of proteins needed for GLUT4 traffic. Our findings reveal a physiological function for F-BAR proteins, supporting a previously unrecognized role for the F-BAR protein CIP4 in GLUT4 endocytosis, and show that interactions between CIP4 and Dynamin-2 and between CIP4 and NWASp are spatially coordinated to promote function.
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Affiliation(s)
- Sean M Hartig
- Division of Pediatrics, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
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7
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Chitu V, Stanley ER. Pombe Cdc15 homology (PCH) proteins: coordinators of membrane-cytoskeletal interactions. Trends Cell Biol 2007; 17:145-56. [PMID: 17296299 DOI: 10.1016/j.tcb.2007.01.003] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2006] [Revised: 12/20/2006] [Accepted: 01/25/2007] [Indexed: 12/27/2022]
Abstract
Cellular adhesion, motility, endocytosis, exocytosis and cytokinesis involve the coordinated reorganization of the cytoskeleton and of the plasma membrane. The 'Pombe Cdc15 homology' (PCH) family of adaptor proteins has recently been shown to coordinate the membrane and cytoskeletal dynamics involved in these processes by curving membranes, recruiting dynamin and controlling the architecture of the actin cytoskeleton. Mutations in PCH family members or proteins that interact with them are associated with autoinflammatory, neurological or neoplastic diseases. Here, we review the nature, actions and disease associations of the vertebrate PCH family members, highlighting their fundamental roles in the regulation of processes involving membrane-cytoskeletal interactions.
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Affiliation(s)
- Violeta Chitu
- Department of Developmental Biology and Molecular Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York, NY 10461, USA
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8
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Aspenström P, Fransson A, Richnau N. Pombe Cdc15 homology proteins: regulators of membrane dynamics and the actin cytoskeleton. Trends Biochem Sci 2006; 31:670-9. [PMID: 17074490 DOI: 10.1016/j.tibs.2006.10.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2006] [Revised: 09/21/2006] [Accepted: 10/18/2006] [Indexed: 11/18/2022]
Abstract
Pombe Cdc15 homology (PCH) proteins have emerged in many species as important coordinators of signalling pathways that regulate actomyosin assembly and membrane dynamics. For example, the prototype PCH protein, Cdc15p of Schizosaccharomyces pombe, has a role in assembly of the contractile ring, which is needed to separate dividing cells. Recently, mammalian PCH proteins have been found to bind phospholipids and to participate in membrane deformation. These findings suggest that PCH proteins are crucial linkers of membrane dynamics and actin polymerization, for example, during the internalization of transmembrane receptors. Intriguingly, some members of the PCH protein family are mutated in neurodegenerative and inflammatory diseases, which has implications for the identification of cures for such disorders.
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Affiliation(s)
- Pontus Aspenström
- Ludwig Institute for Cancer Research, Biomedical Center, Uppsala University, SE-751 24 Uppsala, Sweden.
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9
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Zhang D, Zhou W, Yin C, Chen W, Ozawa R, Ang LH, Anandan L, Aigaki T, Hing H. Misexpression screen for genes altering the olfactory map in Drosophila. Genesis 2006; 44:189-201. [PMID: 16607613 DOI: 10.1002/dvg.20202] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Despite the identification of a number of guidance molecules, a comprehensive picture has yet to emerge to explain the precise anatomy of the olfactory map. From a misexpression screen of 1,515 P{GS} lines, we identified 23 genes that, when forcibly expressed in the olfactory receptor neurons, disrupted the stereotyped anatomy of the Drosophila antennal lobes. These genes, which have not been shown previously to control olfactory map development, encode novel proteins as well as proteins with known roles in axonal outgrowth and cytoskeletal remodeling. We analyzed Akap200, which encodes a Protein Kinase A-binding protein. Overexpression of Akap200 resulted in fusion of the glomeruli, while its loss resulted in misshapen and ectopic glomeruli. The requirement of Akap200 validates our screen as an effective approach for recovering genes controlling glomerular map patterning. Our finding of diverse classes of genes reveals the complexity of the mechanisms that underlie olfactory map development.
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Affiliation(s)
- Dongsheng Zhang
- Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601 South Goodwin Avenue, Urbana, IL 61801, USA
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10
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Tsuji E, Tsuji Y, Fujiwara T, Ogata S, Tsukamoto K, Saku K. Splicing variant of Cdc42 interacting protein-4 disrupts beta-catenin-mediated cell-cell adhesion: expression and function in renal cell carcinoma. Biochem Biophys Res Commun 2005; 339:1083-8. [PMID: 16343437 DOI: 10.1016/j.bbrc.2005.11.117] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2005] [Accepted: 11/17/2005] [Indexed: 11/28/2022]
Abstract
We have identified an alternative splicing variant in the Cdc42-interacting protein 4 (CIP4) gene in patients with renal cell carcinoma (RCC); almost 50% of the RCCs examined showed an aberrant splicing event in reverse transcription-PCR and the insertion of 19 nucleotides derived from intron9 based on a sequence analysis. This variant (CIP4-V) encodes a premature stop codon, resulting in the loss of a tyrosine phosphorylation site, the Cdc42 binding domain, and the SH3 domain. In this report, we show that overexpression of CIP4-V causes the formation of ubiquitinated aggresomes and a loss of cell-cell adhesion. We determined that CIP4-V increased the beta-catenin tyrosine phosphorylation levels that mediate Fer/Fyn tyrosine kinases and induced beta-catenin mistrafficking from cell membrane to cytoplasmic aggresome. These results indicate that CIP4 is critical for beta-catenin-mediated cell-cell adhesion and may be an important aspect of its functional contribution to RCC, especially with regard to metastasis and invasiveness.
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11
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Heiska L, Carpén O. Src phosphorylates ezrin at tyrosine 477 and induces a phosphospecific association between ezrin and a kelch-repeat protein family member. J Biol Chem 2004; 280:10244-52. [PMID: 15623525 DOI: 10.1074/jbc.m411353200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ezrin, a linker between plasma membrane and actin cytoskeleton possesses morphogenic properties and can promote dissemination of tumor cells. Ezrin is phosphorylated on tyrosine, but a detailed picture of the signaling pathways involved in this modification is lacking. The transforming tyrosine kinase Src has various cytoskeletal substrates and is involved in regulation of cellular adhesion. We studied the role of Src in tyrosine phosphorylation of ezrin in adherent cells. We show that ezrin is phosphorylated in human embryonic kidney 293 cells in a Src family-dependent way. In SYF cells lacking Src, Yes, and Fyn, ezrin was not tyrosine-phosphorylated but reintroduction of wild-type Src followed by Src activation or introduction of active Src restored phosphorylation. Mapping of the Src-catalyzed tyrosine in vitro and in vivo by site-directed mutagenesis demonstrated Tyr(477) as the primary target residue. We generated a pTyr(477)-phosphospecific antibody, which confirmed that Tyr(477) becomes phosphorylated in cells in a Src-dependent manner. Tyr(477) phosphorylation did not affect ezrin head-to-tail association or phosphorylation of ezrin on threonine 566, indicating that the function of Tyr(477) phosphorylation is not related to the intramolecular regulation of ezrin. A modified yeast two-hybrid screen in which ezrin bait was phosphorylated by Src identified a novel interaction with a kelch-repeat protein family member, KBTBD2 (Kelch-repeat and BTB/POZ domain containing 2). The Src dependence of the interaction was further verified by affinity precipitation assays. Identification of a functional interplay with Src opens novel avenues for further characterization of the biological activities of ezrin.
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Affiliation(s)
- Leena Heiska
- Department of Pathology, Neuroscience Program, Biomedicum Helsinki, University of Helsinki and Helsinki University Hospital, FIN-00014 Helsinki, Finland
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Larocca MC, Shanks RA, Tian L, Nelson DL, Stewart DM, Goldenring JR. AKAP350 interaction with cdc42 interacting protein 4 at the Golgi apparatus. Mol Biol Cell 2004; 15:2771-81. [PMID: 15047863 PMCID: PMC420101 DOI: 10.1091/mbc.e03-10-0757] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The A kinase anchoring protein 350 (AKAP350) is a multiply spliced type II protein kinase A anchoring protein that localizes to the centrosomes in most cells and to the Golgi apparatus in epithelial cells. In the present study, we sought to identify AKAP350 interacting proteins that could yield insights into AKAP350 function at the Golgi apparatus. Using yeast two-hybrid and pull-down assays, we found that AKAP350 interacts with a family of structurally related proteins, including FBP17, FBP17b, and cdc42 interacting protein 4 (CIP4). CIP4 interacts with the GTP-bound form of cdc42, with the Wiscott Aldrich Syndrome group of proteins, and with microtubules, and exerts regulatory effects on cytoskeleton and membrane trafficking. CIP4 is phosphorylated by protein kinase A in vitro, and elevation of intracellular cyclic AMP with forskolin stimulates in situ phosphorylation of CIP4. Our results indicate that CIP4 interacts with AKAP350 at the Golgi apparatus and that either disruption of this interaction by expressing the CIP4 binding domain in AKAP350, or reduction of AKAP350 expression by RNA interference leads to changes in Golgi structure. The results suggest that AKAP350 and CIP4 influence the maintenance of normal Golgi apparatus structure.
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Affiliation(s)
- M Cecilia Larocca
- Department of Surgery, Vanderbilt University School of Medicine, Vanderbilt-Ingram Cancer Center, and the Nashville VA Medical Center, Nashville, Tennessee 37232, USA
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13
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Dombrosky-Ferlan P, Grishin A, Botelho RJ, Sampson M, Wang L, Rudert WA, Grinstein S, Corey SJ. Felic (CIP4b), a novel binding partner with the Src kinase Lyn and Cdc42, localizes to the phagocytic cup. Blood 2003; 101:2804-9. [PMID: 12456510 DOI: 10.1182/blood-2002-03-0851] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Through its Src homology 3 (SH3) and SH2 domains, the Src kinase Lyn interacts with a small number of phosphoproteins, such as Shc, Cbl, and Vav, which regulate cell cycle and the cytoskeleton. Using Lyn's Unique, SH3, and SH2 domains as bait in a yeast 2-hybrid screen, we isolated a novel gene product with features of a scaffolding protein. We named it Felic because it contains a domain homologous to the tyrosine kinase Fes and the cytoskeletal protein ezrin and forms a Lyn interaction with the GTPase Cdc42 (Felic). Felic was expressed in both hematopoietic and nonhematopoietic tissues. Because it represents an alternative splice product related to the Cdc42-interacting protein 4, CIP4, we also refer to Felic as CIP4b. Felic contains an SH3 recognition site RXPXXP and multiple tyrosine residues. In insulin or serum-stimulated HEK293 cells, Felic became tyrosine phosphorylated. Like CIP4, Felic associated with Cdc42 in its activated form only. Unlike CIP4, Felic does not possess a C-terminal SH3 domain. Coprecipitation studies show that Felic bound to Lyn or activated forms of Cdc42. Overexpression of Felic or CIP4 inhibited NIH 3T3 cell invasiveness in a Matrigel assay. Because Lyn and Cdc42 are involved in phagocytosis, we examined the distribution of Felic in RAW macrophages during particle ingestion. Felic was recruited more efficiently than CIP4 to the phagocytic cups. Altogether, these data suggest that CIP4/Felic constitute a novel family of cytoskeletal scaffolding proteins, integrating Src and Cdc42 pathways. The absence of an SH3 domain in Felic provides a structural basis for functional differences.
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