1
|
Zhang X, Pizzoni A, Hong K, Naim N, Qi C, Korkhov V, Altschuler DL. CAP1 binds and activates adenylyl cyclase in mammalian cells. Proc Natl Acad Sci U S A 2021; 118:e2024576118. [PMID: 34099549 PMCID: PMC8214675 DOI: 10.1073/pnas.2024576118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
CAP1 (Cyclase-Associated Protein 1) is highly conserved in evolution. Originally identified in yeast as a bifunctional protein involved in Ras-adenylyl cyclase and F-actin dynamics regulation, the adenylyl cyclase component seems to be lost in mammalian cells. Prompted by our recent identification of the Ras-like small GTPase Rap1 as a GTP-independent but geranylgeranyl-specific partner for CAP1, we hypothesized that CAP1-Rap1, similar to CAP-Ras-cyclase in yeast, might play a critical role in cAMP dynamics in mammalian cells. In this study, we report that CAP1 binds and activates mammalian adenylyl cyclase in vitro, modulates cAMP in live cells in a Rap1-dependent manner, and affects cAMP-dependent proliferation. Utilizing deletion and mutagenesis approaches, we mapped the interaction of CAP1-cyclase with CAP's N-terminal domain involving critical leucine residues in the conserved RLE motifs and adenylyl cyclase's conserved catalytic loops (e.g., C1a and/or C2a). When combined with a FRET-based cAMP sensor, CAP1 overexpression-knockdown strategies, and the use of constitutively active and negative regulators of Rap1, our studies highlight a critical role for CAP1-Rap1 in adenylyl cyclase regulation in live cells. Similarly, we show that CAP1 modulation significantly affected cAMP-mediated proliferation in an RLE motif-dependent manner. The combined study indicates that CAP1-cyclase-Rap1 represents a regulatory unit in cAMP dynamics and biology. Since Rap1 is an established downstream effector of cAMP, we advance the hypothesis that CAP1-cyclase-Rap1 represents a positive feedback loop that might be involved in cAMP microdomain establishment and localized signaling.
Collapse
Affiliation(s)
- Xuefeng Zhang
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Alejandro Pizzoni
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Kyoungja Hong
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Nyla Naim
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Chao Qi
- Institute of Molecular Biology and Biophysics, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - Volodymyr Korkhov
- Institute of Molecular Biology and Biophysics, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - Daniel L Altschuler
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261;
| |
Collapse
|
2
|
Zhang X, Cao S, Barila G, Edreira MM, Hong K, Wankhede M, Naim N, Buck M, Altschuler DL. Cyclase-associated protein 1 (CAP1) is a prenyl-binding partner of Rap1 GTPase. J Biol Chem 2018; 293:7659-7673. [PMID: 29618512 PMCID: PMC5961064 DOI: 10.1074/jbc.ra118.001779] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 02/22/2018] [Indexed: 12/20/2022] Open
Abstract
Rap1 proteins are members of the Ras subfamily of small GTPases involved in many biological responses, including adhesion, cell proliferation, and differentiation. Like all small GTPases, they work as molecular allosteric units that are active in signaling only when associated with the proper membrane compartment. Prenylation, occurring in the cytosol, is an enzymatic posttranslational event that anchors small GTPases at the membrane, and prenyl-binding proteins are needed to mask the cytoplasm-exposed lipid during transit to the target membrane. However, several of these proteins still await discovery. In this study, we report that cyclase-associated protein 1 (CAP1) binds Rap1. We found that this binding is GTP-independent, does not involve Rap1's effector domain, and is fully contained in its C-terminal hypervariable region (HVR). Furthermore, Rap1 prenylation was required for high-affinity interactions with CAP1 in a geranylgeranyl-specific manner. The prenyl binding specifically involved CAP1's C-terminal hydrophobic β-sheet domain. We present a combination of experimental and computational approaches, yielding a model whereby the high-affinity binding between Rap1 and CAP1 involves electrostatic and nonpolar side-chain interactions between Rap1's HVR residues, lipid, and CAP1 β-sheet domain. The binding was stabilized by the lipid insertion into the β-solenoid whose interior was occupied by nonpolar side chains. This model was reminiscent of the recently solved structure of the PDEδ-K-Ras complex; accordingly, disruptors of this complex, e.g. deltarasin, blocked the Rap1-CAP1 interaction. These findings indicate that CAP1 is a geranylgeranyl-binding partner of Rap1.
Collapse
Affiliation(s)
- Xuefeng Zhang
- From the Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 and
| | - Shufen Cao
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44116
| | - Guillermo Barila
- From the Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 and
| | - Martin M Edreira
- From the Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 and
| | - Kyoungja Hong
- From the Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 and
| | - Mamta Wankhede
- From the Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 and
| | - Nyla Naim
- From the Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 and
| | - Matthias Buck
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44116
| | - Daniel L Altschuler
- From the Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261 and
| |
Collapse
|
3
|
The C-terminal dimerization motif of cyclase-associated protein is essential for actin monomer regulation. Biochem J 2016; 473:4427-4441. [PMID: 27729544 DOI: 10.1042/bcj20160329] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 09/22/2016] [Accepted: 10/11/2016] [Indexed: 12/31/2022]
Abstract
Cyclase-associated protein (CAP) is a conserved actin-regulatory protein that functions together with actin depolymerizing factor (ADF)/cofilin to enhance actin filament dynamics. CAP has multiple functional domains, and the function to regulate actin monomers is carried out by its C-terminal half containing a Wiskott-Aldrich Syndrome protein homology 2 (WH2) domain, a CAP and X-linked retinitis pigmentosa 2 (CARP) domain, and a dimerization motif. WH2 and CARP are implicated in binding to actin monomers and important for enhancing filament turnover. However, the role of the dimerization motif is unknown. Here, we investigated the function of the dimerization motif of CAS-2, a CAP isoform in the nematode Caenorhabditis elegans, in actin monomer regulation. CAS-2 promotes ATP-dependent recycling of ADF/cofilin-bound actin monomers for polymerization by enhancing exchange of actin-bound nucleotides. The C-terminal half of CAS-2 (CAS-2C) has nearly as strong activity as full-length CAS-2. Maltose-binding protein (MBP)-tagged CAS-2C is a dimer. However, MBP-CAS-2C with a truncation of either one or two C-terminal β-strands is monomeric. Truncations of the dimerization motif in MBP-CAS-2C nearly completely abolish its activity to sequester actin monomers from polymerization and enhance nucleotide exchange on actin monomers. As a result, these CAS-2C variants, also in the context of full-length CAS-2, fail to compete with ADF/cofilin to release actin monomers for polymerization. CAS-2C variants lacking the dimerization motif exhibit enhanced binding to actin filaments, which is mediated by WH2. Taken together, these results suggest that the evolutionarily conserved dimerization motif of CAP is essential for its C-terminal region to exert the actin monomer-specific regulatory function.
Collapse
|
4
|
Chen M, Zheng T, Han S, Zhang L, Bai Y, Fang X, Ding SZ, Yang Y. A preliminary study of plasma cyclase-associated protein 2 as a novel biomarker for early stage and alpha-fetoprotein negative hepatocellular carcinoma patients. Clin Res Hepatol Gastroenterol 2015; 39:215-21. [PMID: 25312778 DOI: 10.1016/j.clinre.2014.08.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 08/03/2014] [Accepted: 08/18/2014] [Indexed: 02/06/2023]
Abstract
BACKGROUND AND OBJECTIVE Cyclase-associated protein 2 (CAP2) has recently been suggested to be a candidate biomarker for hepatocellular carcinoma (HCC). We aim to investigate the application of CAP2 as a novel biomarker for HCC patients especially for those at early stage and are AFP-negative. METHODS The CAP2 and AFP plasma levels were analyzed by enzyme-linked-immunosorbent assay in 86 HCC, 59 cirrhotic patients, and 30 normal individuals. Their correlation with HCC tumor behavior, disease stages, diagnostic sensitivity, specificity and accuracy were analyzed. RESULTS The results showed that both CAP2 and AFP plasma levels in HCC patients were significantly elevated when compared to cirrhosis and controls. CAP2 levels correlate well with HCC patient's histological grade, clinical stage and tumor size, but not with patient's age, gender, hepatitis B virus infection status and plasma AFP level. CAP2 had better sensitivity as compared to AFP (82.6% vs 59.3%) for general HCC, and early stage of HCC patients (78.6% vs 40.4%). In addition, CAP2 is able to complement AFP to predict 82.9% of HCC in AFP-negative patients. CONCLUSION We suggest that CAP2 is a novel biomarker for HCC patient, this may be especially useful for detection of early stage HCC and when plasma AFP level is negative.
Collapse
Affiliation(s)
- Ming Chen
- Department of Gastroenterology and Hepatology, Henan Provincial People's Hospital, Zhengzhou University, Zhengzhou, Henan 450003, PR China
| | - Tenghao Zheng
- Department of Gastroenterology and Hepatology, Henan Provincial People's Hospital, Zhengzhou University, Zhengzhou, Henan 450003, PR China
| | - Shuangyin Han
- Department of Gastroenterology and Hepatology, Henan Provincial People's Hospital, Zhengzhou University, Zhengzhou, Henan 450003, PR China
| | - Lida Zhang
- Department of Gastroenterology and Hepatology, Henan Provincial People's Hospital, Zhengzhou University, Zhengzhou, Henan 450003, PR China
| | - Yangqiu Bai
- Department of Gastroenterology and Hepatology, Henan Provincial People's Hospital, Zhengzhou University, Zhengzhou, Henan 450003, PR China
| | - Xinhui Fang
- Department of Gastroenterology and Hepatology, Henan Provincial People's Hospital, Zhengzhou University, Zhengzhou, Henan 450003, PR China
| | - Song-Ze Ding
- Department of Gastroenterology and Hepatology, Henan Provincial People's Hospital, Zhengzhou University, Zhengzhou, Henan 450003, PR China
| | - Yuxiu Yang
- Department of Gastroenterology and Hepatology, Henan Provincial People's Hospital, Zhengzhou University, Zhengzhou, Henan 450003, PR China.
| |
Collapse
|
5
|
Hua M, Yan S, Deng Y, Xi Q, Liu R, Yang S, Liu J, Tang C, Wang Y, Zhong J. CAP1 is overexpressed in human epithelial ovarian cancer and promotes cell proliferation. Int J Mol Med 2015; 35:941-9. [PMID: 25652936 PMCID: PMC4356442 DOI: 10.3892/ijmm.2015.2089] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 01/27/2015] [Indexed: 01/07/2023] Open
Abstract
Adenylate cyclase-associated protein 1 (CAP1) regulates both actin filaments and the Ras/cAMP pathway in yeast, and has been found play a role in cell motility and in the development of certain types of cancer. In the present study, we investigated CAP1 gene expression in human epithelial ovarian cancer (EOC). Western blot analysis and immunohistochemistry were performed using EOC tissue samples and the results revealed that CAP1 expression increased with the increasing grade of EOC. In the normal ovarian tissue samples however, CAP1 expression was barely detected. Using Pearson’s χ2 test, it was demonstrated that CAP1 expression was associated with the histological grade and Ki-67 expression. Kaplan-Meier analysis revealed that a higher CAP1 expression in patients with EOC was associated with a poorer prognosis. In in vitro experiments using HO-8910 EOC cells, the expression of CAP1 was knocked down using siRNA. The proliferation of the HO-8910 cells was then determined by cell cycle analysis and cell proliferation assay using the cell counting kit-8 and flow cytometry. The results revealed that the loss of CAP1 expression inhibited cell cycle progression. These findings suggest that a high expression of CAP1 is involved in the pathogenesis of EOC, and that the downregulation of CAP1 in tumor cells may be a therapeutic target for the treatment of patients with EOC.
Collapse
Affiliation(s)
- Minhui Hua
- Department of Obstetrics and Gynecology, Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Sujuan Yan
- Department of Obstetrics and Gynecology, Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Yan Deng
- Department of Obstetrics and Gynecology, Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Qinghua Xi
- Department of Obstetrics and Gynecology, Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Rong Liu
- Department of Oncology, Nantong University Cancer Hospital, Nantong, Jiangsu 226001, P.R. China
| | - Shuyun Yang
- Department of Pathology, Nantong University Cancer Hospital, Nantong, Jiangsu 226001, P.R. China
| | - Jian Liu
- Department of Obstetrics and Gynecology, Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Chunhui Tang
- Department of Obstetrics and Gynecology, Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Yingying Wang
- Department of Pathogen Biology, Medical College, Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Jianxin Zhong
- Department of Obstetrics and Gynecology, Affiliated Hospital of Nantong University, Nantong, Jiangsu 226001, P.R. China
| |
Collapse
|
6
|
Zhou GL, Zhang H, Wu H, Ghai P, Field J. Phosphorylation of the cytoskeletal protein CAP1 controls its association with cofilin and actin. J Cell Sci 2014; 127:5052-65. [PMID: 25315833 DOI: 10.1242/jcs.156059] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Cell signaling can control the dynamic balance between filamentous and monomeric actin by modulating actin regulatory proteins. One family of actin regulating proteins that controls actin dynamics comprises cyclase-associated proteins 1 and 2 (CAP1 and 2, respectively). However, cell signals that regulate CAPs remained unknown. We mapped phosphorylation sites on mouse CAP1 and found S307 and S309 to be regulatory sites. We further identified glycogen synthase kinase 3 as a kinase phosphorylating S309. The phosphomimetic mutant S307D/S309D lost binding to its partner cofilin and, when expressed in cells, caused accumulation of actin stress fibers similar to that in cells with reduced CAP expression. In contrast, the non-phosphorylatable S307A/S309A mutant showed drastically increased cofilin binding and reduced binding to actin. These results suggest that the phosphorylation serves to facilitate release of cofilin for a subsequent cycle of actin filament severing. Moreover, our results suggest that S307 and S309 function in tandem; neither the alterations in binding cofilin and/or actin, nor the defects in rescuing the phenotype of the enlarged cell size in CAP1 knockdown cells was observed in point mutants of either S307 or S309. In summary, we identify a novel regulatory mechanism of CAP1 through phosphorylation.
Collapse
Affiliation(s)
- Guo-Lei Zhou
- Department of Biological Sciences, Arkansas State University, State University, AR 72467, USA Molecular Biosciences Program, Arkansas State University, State University, AR 72467, USA
| | - Haitao Zhang
- Department of Biological Sciences, Arkansas State University, State University, AR 72467, USA Molecular Biosciences Program, Arkansas State University, State University, AR 72467, USA
| | - Huhehasi Wu
- Department of Biological Sciences, Arkansas State University, State University, AR 72467, USA
| | - Pooja Ghai
- Department of Biological Sciences, Arkansas State University, State University, AR 72467, USA Molecular Biosciences Program, Arkansas State University, State University, AR 72467, USA
| | - Jeffrey Field
- Department of Pharmacology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| |
Collapse
|
7
|
Ono S. The role of cyclase-associated protein in regulating actin filament dynamics - more than a monomer-sequestration factor. J Cell Sci 2014; 126:3249-58. [PMID: 23908377 DOI: 10.1242/jcs.128231] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Dynamic reorganization of the actin cytoskeleton is fundamental to a number of cell biological events. A variety of actin-regulatory proteins modulate polymerization and depolymerization of actin and contribute to actin cytoskeletal reorganization. Cyclase-associated protein (CAP) is a conserved actin-monomer-binding protein that has been studied for over 20 years. Early studies have shown that CAP sequesters actin monomers; recent studies, however, have revealed more active roles of CAP in actin filament dynamics. CAP enhances the recharging of actin monomers with ATP antagonistically to ADF/cofilin, and also promotes the severing of actin filaments in cooperation with ADF/cofilin. Self-oligomerization and binding to other proteins regulate activities and localization of CAP. CAP has crucial roles in cell signaling, development, vesicle trafficking, cell migration and muscle sarcomere assembly. This Commentary discusses the recent advances in our understanding of the functions of CAP and its implications as an important regulator of actin cytoskeletal dynamics, which are involved in various cellular activities.
Collapse
Affiliation(s)
- Shoichiro Ono
- Department of Pathology and Department of Cell Biology, Emory University, Atlanta, GA 30322, USA.
| |
Collapse
|
8
|
Crabbé A, Nielsen-Preiss SM, Woolley CM, Barrila J, Buchanan K, McCracken J, Inglis DO, Searles SC, Nelman-Gonzalez MA, Ott CM, Wilson JW, Pierson DL, Stefanyshyn-Piper HM, Hyman LE, Nickerson CA. Spaceflight enhances cell aggregation and random budding in Candida albicans. PLoS One 2013; 8:e80677. [PMID: 24324620 PMCID: PMC3851762 DOI: 10.1371/journal.pone.0080677] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 10/07/2013] [Indexed: 12/24/2022] Open
Abstract
This study presents the first global transcriptional profiling and phenotypic characterization of the major human opportunistic fungal pathogen, Candida albicans, grown in spaceflight conditions. Microarray analysis revealed that C. albicans subjected to short-term spaceflight culture differentially regulated 452 genes compared to synchronous ground controls, which represented 8.3% of the analyzed ORFs. Spaceflight-cultured C. albicans–induced genes involved in cell aggregation (similar to flocculation), which was validated by microscopic and flow cytometry analysis. We also observed enhanced random budding of spaceflight-cultured cells as opposed to bipolar budding patterns for ground samples, in accordance with the gene expression data. Furthermore, genes involved in antifungal agent and stress resistance were differentially regulated in spaceflight, including induction of ABC transporters and members of the major facilitator family, downregulation of ergosterol-encoding genes, and upregulation of genes involved in oxidative stress resistance. Finally, downregulation of genes involved in actin cytoskeleton was observed. Interestingly, the transcriptional regulator Cap1 and over 30% of the Cap1 regulon was differentially expressed in spaceflight-cultured C. albicans. A potential role for Cap1 in the spaceflight response of C. albicans is suggested, as this regulator is involved in random budding, cell aggregation, and oxidative stress resistance; all related to observed spaceflight-associated changes of C. albicans. While culture of C. albicans in microgravity potentiates a global change in gene expression that could induce a virulence-related phenotype, no increased virulence in a murine intraperitoneal (i.p.) infection model was observed under the conditions of this study. Collectively, our data represent an important basis for the assessment of the risk that commensal flora could play during human spaceflight missions. Furthermore, since the low fluid-shear environment of microgravity is relevant to physical forces encountered by pathogens during the infection process, insights gained from this study could identify novel infectious disease mechanisms, with downstream benefits for the general public.
Collapse
Affiliation(s)
- Aurélie Crabbé
- Center for Infectious Diseases and Vaccinology, The Biodesign Institute, Arizona State University, Tempe, Arizona, United States of America
| | - Sheila M. Nielsen-Preiss
- Department of Immunology and Infectious Disease, Montana State University, Bozeman, Montanta, United States of America
| | - Christine M. Woolley
- Department of Immunology and Infectious Disease, Montana State University, Bozeman, Montanta, United States of America
| | - Jennifer Barrila
- Center for Infectious Diseases and Vaccinology, The Biodesign Institute, Arizona State University, Tempe, Arizona, United States of America
| | - Kent Buchanan
- Department of Biology, Oklahoma City University, Oklahoma City, Oklahoma, United States of America
- Department of Microbiology and Immunology, Program in Molecular Pathogenesis and Immunity, Tulane University Health Sciences Center, New Orleans, Louisiana, United States of America
| | - James McCracken
- Department of Microbiology and Immunology, Program in Molecular Pathogenesis and Immunity, Tulane University Health Sciences Center, New Orleans, Louisiana, United States of America
- Diabetes and Obesity Center, University of Louisville, Louisville, Kentucky, United States of America
| | - Diane O. Inglis
- Department of Genetics, Stanford University Medical School, Stanford, California, United States of America
| | - Stephen C. Searles
- Department of Immunology and Infectious Disease, Montana State University, Bozeman, Montanta, United States of America
| | | | - C. Mark Ott
- Biomedical Research and Environmental Sciences Division, NASA Johnson Space Center, Houston, Texas, United States of America
| | - James W. Wilson
- Center for Infectious Diseases and Vaccinology, The Biodesign Institute, Arizona State University, Tempe, Arizona, United States of America
- Department of Microbiology and Immunology, Program in Molecular Pathogenesis and Immunity, Tulane University Health Sciences Center, New Orleans, Louisiana, United States of America
- Department of Biology, Villanova University, Villanova, Pennsylvania, United States of America
| | - Duane L. Pierson
- Biomedical Research and Environmental Sciences Division, NASA Johnson Space Center, Houston, Texas, United States of America
| | | | - Linda E. Hyman
- Department of Immunology and Infectious Disease, Montana State University, Bozeman, Montanta, United States of America
- Boston University School of Medicine, Boston, Massachusetts, United States of America
| | - Cheryl A. Nickerson
- School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
- Center for Infectious Diseases and Vaccinology, The Biodesign Institute, Arizona State University, Tempe, Arizona, United States of America
- Department of Microbiology and Immunology, Program in Molecular Pathogenesis and Immunity, Tulane University Health Sciences Center, New Orleans, Louisiana, United States of America
- * E-mail:
| |
Collapse
|
9
|
Lin CM, Lin PY, Li YC, Hsu JC. Capulet and Slingshot share overlapping functions during Drosophila eye morphogenesis. J Biomed Sci 2012; 19:46. [PMID: 22545588 PMCID: PMC3411472 DOI: 10.1186/1423-0127-19-46] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Accepted: 04/30/2012] [Indexed: 02/05/2023] Open
Abstract
Background CAP/Capulet (Capt), Slingshot (Ssh) and Cofilin/Twinstar (Tsr) are actin-binding proteins that restrict actin polymerization. Previously, it was shown that low resolution analyses of loss-of-function mutations in capt, ssh and tsr all show ectopic F-actin accumulation in various Drosophila tissues. In contrast, RNAi depletion of capt, tsr and ssh in Drosophila S2 cells all affect actin-based lamella formation differently. Whether loss of these three related genes might cause the same effect in the same tissue remains unclear. Methods Loss-of-function mutant clones were generated using the MARCM or EGUF system whereas overexpression clones were generated using the Flip-out system. Immunostaining were then performed in eye imaginal discs with clones. FRAP was performed in cultured eye discs. Results Here, we compared their loss-of-function phenotype at single-cell resolution, using a sheet of epithelial cells in the Drosophila eye imaginal disc as a model system. Surprisingly, we found that capt and ssh, but not tsr, mutant cells within and posterior to the morphogenetic furrow (MF) shared similar phenotypes. The capt/ssh mutant cells possessed: (1) hexagonal cell packing with discontinuous adherens junctions; and (2) largely complementary accumulation of excessive phosphorylated myosin light chain (p-MLC) and F-actin rings at the apical cortex. We further showed that the capt/ssh mutant phenotypes depended on the inactivation of protein kinase A (PKA) and activation of Rho. Conclusions Although Capt, Ssh and Tsr were reported to negatively regulate actin polymerization, we found that Capt and Ssh, but not Tsr, share overlapping functions during eye morphogenesis.
Collapse
Affiliation(s)
- Chiao-Ming Lin
- Institute of Molecular Medicine, Department of Life Science, National Tsing Hua University, Hsinchu, Taiwan 30034, Republic of China
| | | | | | | |
Collapse
|
10
|
Hliscs M, Sattler JM, Tempel W, Artz JD, Dong A, Hui R, Matuschewski K, Schüler H. Structure and function of a G-actin sequestering protein with a vital role in malaria oocyst development inside the mosquito vector. J Biol Chem 2010; 285:11572-83. [PMID: 20083609 DOI: 10.1074/jbc.m109.054916] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Cyclase-associated proteins (CAPs) are evolutionary conserved G-actin-binding proteins that regulate microfilament turnover. CAPs have a modular structure consisting of an N-terminal adenylate cyclase binding domain, a central proline-rich segment, and a C-terminal actin binding domain. Protozoan parasites of the phylum Apicomplexa, such as Cryptosporidium and the malaria parasite Plasmodium, express small CAP orthologs with homology to the C-terminal actin binding domain (C-CAP). Here, we demonstrate by reverse genetics that C-CAP is dispensable for the pathogenic Plasmodium blood stages. However, c-cap(-) parasites display a complete defect in oocyst development in the insect vector. By trans-species complementation we show that the Cryptosporidium parvum ortholog complements the Plasmodium gene functions. Purified recombinant C. parvum C-CAP protein binds actin monomers and prevents actin polymerization. The crystal structure of C. parvum C-CAP shows two monomers with a right-handed beta-helical fold intercalated at their C termini to form the putative physiological dimer. Our results reveal a specific vital role for an apicomplexan G-actin-binding protein during sporogony, the parasite replication phase that precedes formation of malaria transmission stages. This study also exemplifies how Plasmodium reverse genetics combined with biochemical and structural analyses of orthologous proteins can offer a fast track toward systematic gene characterization in apicomplexan parasites.
Collapse
Affiliation(s)
- Marion Hliscs
- Department of Parasitology, Heidelberg University School of Medicine, 69120 Heidelberg, Germany
| | | | | | | | | | | | | | | |
Collapse
|
11
|
Zou H, Fang HM, Zhu Y, Wang Y. Candida albicans Cyr1, Cap1 and G-actin form a sensor/effector apparatus for activating cAMP synthesis in hyphal growth. Mol Microbiol 2009; 75:579-91. [PMID: 19943905 DOI: 10.1111/j.1365-2958.2009.06980.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
A key virulence trait of Candida albicans is its ability to undergo the yeast-to-hyphal growth transition in response to environmental signals. This transition critically requires a rapid activation of the adenylyl cyclase Cyr1 to generate a cAMP spike. However, the identity of the signal sensors and mechanisms of signal processing and integration remain largely unclear. Recent evidence suggests that some sensors are embedded in Cyr1 itself. To test this hypothesis, we asked whether purified Cyr1 can respond to hyphal induction. Here, we report that Cyr1 co-purifies with Cap1 and G-actin as a tripartite complex which can increase cAMP synthesis in response to hyphal inducing signals in an actin-dependent manner. Cap1 binds Cyr1 and G-actin through its N- and C-terminus respectively. Deleting the G-actin binding sites or treating the complex with the actin toxin latrunculin A or cytochalasin A inhibits the activation of cAMP synthesis. Strains expressing Cap1 mutants lacking the G-actin binding site are impaired in both cAMP synthesis and hyphal morphogenesis. Thus, our findings reveal an essentially intact sensor/effector apparatus composed of Cyr1, Cap1 and G-actin. Furthermore, G-actin's regulatory role in this apparatus may prove to be the missing link whereby cellular actin status knowingly influences cAMP-mediated cellular processes.
Collapse
Affiliation(s)
- Hao Zou
- Institute of Molecular and Cell Biology, A *STAR (Agency for Science, Technology and Research), 61 Biopolis Drive, Singapore 138673, Singapore
| | | | | | | |
Collapse
|
12
|
Quintero-Monzon O, Jonasson EM, Bertling E, Talarico L, Chaudhry F, Sihvo M, Lappalainen P, Goode BL. Reconstitution and dissection of the 600-kDa Srv2/CAP complex: roles for oligomerization and cofilin-actin binding in driving actin turnover. J Biol Chem 2009; 284:10923-34. [PMID: 19201756 DOI: 10.1074/jbc.m808760200] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Srv2/cyclase-associated protein is expressed in virtually all plant, animal, and fungal organisms and has a conserved role in promoting actin depolymerizing factor/cofilin-mediated actin turnover. This is achieved by the abilities of Srv2 to recycle cofilin from ADP-actin monomers and to promote nucleotide exchange (ATP for ADP) on actin monomers. Despite this important and universal role in facilitating actin turnover, the mechanism underlying Srv2 function has remained elusive. Previous studies have demonstrated a critical functional role for the G-actin-binding C-terminal half of Srv2. Here we describe an equally important role in vivo for the N-terminal half of Srv2 in driving actin turnover. We pinpoint this activity to a conserved patch of surface residues on the N-terminal dimeric helical folded domain of Srv2, and we show that this functional site interacts with cofilin-actin complexes. Furthermore, we show that this site is essential for Srv2 acceleration of cofilin-mediated actin turnover in vitro. A cognate Srv2-binding site is identified on a conserved surface of cofilin, suggesting that this function likely extends to other organisms. In addition, our analyses reveal that higher order oligomerization of Srv2 depends on its N-terminal predicted coiled coil domain and that oligomerization optimizes Srv2 function in vitro and in vivo. Based on these data, we present a revised model for the mechanism by which Srv2 promotes actin turnover, in which coordinated activities of its N- and C-terminal halves catalyze sequential steps in recycling cofilin and actin monomers.
Collapse
Affiliation(s)
- Omar Quintero-Monzon
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, Massachusetts 02454, USA
| | | | | | | | | | | | | | | |
Collapse
|
13
|
Sultana H, Neelakanta G, Eichinger L, Rivero F, Noegel AA. Microarray phenotyping places cyclase associated protein CAP at the crossroad of signaling pathways reorganizing the actin cytoskeleton in Dictyostelium. Exp Cell Res 2009; 315:127-40. [DOI: 10.1016/j.yexcr.2008.10.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Revised: 08/29/2008] [Accepted: 10/14/2008] [Indexed: 01/31/2023]
|
14
|
Chaudhry F, Guérin C, von Witsch M, Blanchoin L, Staiger CJ. Identification of Arabidopsis cyclase-associated protein 1 as the first nucleotide exchange factor for plant actin. Mol Biol Cell 2007; 18:3002-14. [PMID: 17538023 PMCID: PMC1949352 DOI: 10.1091/mbc.e06-11-1041] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2006] [Revised: 05/17/2007] [Accepted: 05/18/2007] [Indexed: 11/11/2022] Open
Abstract
The actin cytoskeleton powers organelle movements, orchestrates responses to abiotic stresses, and generates an amazing array of cell shapes. Underpinning these diverse functions of the actin cytoskeleton are several dozen accessory proteins that coordinate actin filament dynamics and construct higher-order assemblies. Many actin-binding proteins from the plant kingdom have been characterized and their function is often surprisingly distinct from mammalian and fungal counterparts. The adenylyl cyclase-associated protein (CAP) has recently been shown to be an important regulator of actin dynamics in vivo and in vitro. The disruption of actin organization in cap mutant plants indicates defects in actin dynamics or the regulated assembly and disassembly of actin subunits into filaments. Current models for actin dynamics maintain that actin-depolymerizing factor (ADF)/cofilin removes ADP-actin subunits from filament ends and that profilin recharges these monomers with ATP by enhancing nucleotide exchange and delivery of subunits onto filament barbed ends. Plant profilins, however, lack the essential ability to stimulate nucleotide exchange on actin, suggesting that there might be a missing link yet to be discovered from plants. Here, we show that Arabidopsis thaliana CAP1 (AtCAP1) is an abundant cytoplasmic protein; it is present at a 1:3 M ratio with total actin in suspension cells. AtCAP1 has equivalent affinities for ADP- and ATP-monomeric actin (Kd approximately 1.3 microM). Binding of AtCAP1 to ATP-actin monomers inhibits polymerization, consistent with AtCAP1 being an actin sequestering protein. However, we demonstrate that AtCAP1 is the first plant protein to increase the rate of nucleotide exchange on actin. Even in the presence of ADF/cofilin, AtCAP1 can recharge actin monomers and presumably provide a polymerizable pool of subunits to profilin for addition onto filament ends. In turnover assays, plant profilin, ADF, and CAP act cooperatively to promote flux of subunits through actin filament barbed ends. Collectively, these results and our understanding of other actin-binding proteins implicate CAP1 as a central player in regulating the pool of unpolymerized ATP-actin.
Collapse
Affiliation(s)
- Faisal Chaudhry
- *Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-2064; and
| | - Christophe Guérin
- Institut de Recherches en Technologie et Sciences pour le Vivant (iRTSV), Commissariat à l'Energie Atomique/Centre National de la Recherche Scientifique/Institut National de la Recherche Agronomique/Université Joseph Fourier, Commissariat à l'Energie Atomique Grenoble, F38054 Grenoble, France
| | - Matthias von Witsch
- *Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-2064; and
| | - Laurent Blanchoin
- Institut de Recherches en Technologie et Sciences pour le Vivant (iRTSV), Commissariat à l'Energie Atomique/Centre National de la Recherche Scientifique/Institut National de la Recherche Agronomique/Université Joseph Fourier, Commissariat à l'Energie Atomique Grenoble, F38054 Grenoble, France
| | - Christopher J. Staiger
- *Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-2064; and
| |
Collapse
|
15
|
Yusof AM, Jaenicke E, Pedersen JS, Noegel AA, Schleicher M, Hofmann A. Mechanism of oligomerisation of cyclase-associated protein from Dictyostelium discoideum in solution. J Mol Biol 2006; 362:1072-81. [PMID: 16949609 DOI: 10.1016/j.jmb.2006.08.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Accepted: 08/01/2006] [Indexed: 10/24/2022]
Abstract
Cyclase-associated protein (CAP) is a highly conserved modular protein implicated in the regulation of actin filament dynamics and a variety of developmental and morphological processes. The protein exists as a high molecular weight complex in cell extracts and purified protein possesses a high tendency to aggregate, a major obstacle for crystallisation. Using a mutagenesis approach, we show that two structural features underlie the mechanism of oligomerisation in Dictyostelium discoideum CAP. Positively charged clusters on the surface of the N-terminal helix-barrel domain are involved in inter-molecular interactions with the N or C-terminal domains. Abolishing these interactions mainly renders dimers due to a domain swap feature in the extreme C-terminal region of the protein that was previously described. Based on earlier studies with yeast CAP, we also generated constructs with mutations in the extreme N-terminal region of Dictyostelium CAP that did not show significantly altered oligomerisation behaviour. Constructs with mutations in the earlier identified protein-protein interaction interface on the N-terminal domain of CAP could not be expressed as soluble protein. Assessment of the soluble proteins indicates that the mutations did not affect their overall fold. Further studies point to the correlation between stability of full-length CAP with its multimerisation behaviour, where oligomer formation leads to a more stable protein.
Collapse
Affiliation(s)
- Adlina Mohd Yusof
- Institute of Structural and Molecular Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JR, UK
| | | | | | | | | | | |
Collapse
|
16
|
Yusof AM, Hu NJ, Wlodawer A, Hofmann A. Structural evidence for variable oligomerization of the N-terminal domain of cyclase-associated protein (CAP). Proteins 2006; 58:255-62. [PMID: 15558566 DOI: 10.1002/prot.20314] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Cyclase-associated protein (CAP) is a highly conserved and widely distributed protein that links the nutritional response signaling to cytoskeleton remodeling. In yeast, CAP is a component of the adenylyl cyclase complex and helps to activate the Ras-mediated catalytic cycle of the cyclase. While the N-terminal domain of CAP (N-CAP) provides a binding site for adenylyl cyclase, the C-terminal domain (C-CAP) possesses actin binding activity. Our attempts to crystallize full-length recombinant CAP from Dictyostelium discoideum resulted in growth of orthorhombic crystals containing only the N-terminal domain (residues 42-227) due to auto-proteolytic cleavage. The structure was solved by molecular replacement with data at 2.2 A resolution. The present crystal structure allows the characterization of a head-to-tail N-CAP dimer in the asymmetric unit and a crystallographic side-to-side dimer. Comparison with previously published structures of N-CAP reveals variable modes of dimerization of this domain, but the presence of a common interface for the side-to-side dimer.
Collapse
Affiliation(s)
- Adlina Mohd Yusof
- Institute of Structural & Molecular Biology, School of Biological Sciences, The University of Edinburgh, Scotland, United Kingdom
| | | | | | | |
Collapse
|
17
|
Bahn YS, Hicks JK, Giles SS, Cox GM, Heitman J. Adenylyl cyclase-associated protein Aca1 regulates virulence and differentiation of Cryptococcus neoformans via the cyclic AMP-protein kinase A cascade. EUKARYOTIC CELL 2005; 3:1476-91. [PMID: 15590822 PMCID: PMC539029 DOI: 10.1128/ec.3.6.1476-1491.2004] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The evolutionarily conserved cyclic AMP (cAMP) signaling pathway controls cell functions in response to environmental cues in organisms as diverse as yeast and mammals. In the basidiomycetous human pathogenic fungus Cryptococcus neoformans, the cAMP pathway governs virulence and morphological differentiation. Here we identified and characterized adenylyl cyclase-associated protein, Aca1, which functions in parallel with the Galpha subunit Gpa1 to control the adenylyl cyclase (Cac1). Aca1 interacted with the C terminus of Cac1 in the yeast two-hybrid system. By molecular and genetic approaches, Aca1 was shown to play a critical role in mating by regulating cell fusion and filamentous growth in a cAMP-dependent manner. Aca1 also regulates melanin and capsule production via the Cac1-cAMP-protein kinase A pathway. Genetic epistasis studies support models in which Aca1 and Gpa1 are necessary and sufficient components that cooperate to activate adenylyl cyclase. Taken together, these studies further define the cAMP signaling cascade controlling virulence of this ubiquitous human fungal pathogen.
Collapse
Affiliation(s)
- Yong-Sun Bahn
- Department of Molecular Genetics and Microbiology, 322 CARL Bldg., Box 3546, Research Dr., Duke University Medical Center, Durham, NC 27710, USA
| | | | | | | | | |
Collapse
|
18
|
Abstract
The dendritic nucleation model was devised to explain the cycle of actin dynamics resulting in actin filament network assembly and disassembly in two contexts--at the leading edge of motile cells and in the actin comet tails of intracellular pathogenic bacteria and viruses. Due to the detailed nature of its biochemical predictions, the model has provided an excellent focus for subsequent experimentation. This review summarizes recent work on actin dynamics in the context of the dendritic nucleation model. One outcome of this research is the possibility that additional proteins, as well as the six proteins included in the original model, might increase the efficiency of dendritic nucleation or modify the resulting actin network. In addition, actin dynamics at the leading edge might be influenced by a second actin filament network, independent of dendritic nucleation.
Collapse
|
19
|
Dodatko T, Fedorov AA, Grynberg M, Patskovsky Y, Rozwarski DA, Jaroszewski L, Aronoff-Spencer E, Kondraskina E, Irving T, Godzik A, Almo SC. Crystal structure of the actin binding domain of the cyclase-associated protein. Biochemistry 2004; 43:10628-41. [PMID: 15311924 DOI: 10.1021/bi049071r] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cyclase-associated protein (CAP or Srv2p) is a modular actin monomer binding protein that directly regulates filament dynamics and has been implicated in a number of complex developmental and morphological processes, including mRNA localization and the establishment of cell polarity. The crystal structure of the C-terminal dimerization and actin monomer binding domain (C-CAP) reveals a highly unusual dimer, composed of monomers possessing six coils of right-handed beta-helix flanked by antiparallel beta-strands. Domain swapping, involving the last two strands of each monomer, results in the formation of an extended dimer with an extensive interface. This structural and biochemical characterization provides new insights into the organization and potential mechanistic properties of the multiprotein assemblies that integrate dynamic actin processes into the overall physiology of the cell. An unanticipated finding is that the unique tertiary structure of the C-CAP monomer provides a structural model for a wide range of molecules, including RP2 and cofactor C, proteins involved in X-linked retinitis pigmentosa and tubulin maturation, respectively, as well as several uncharacterized proteins that exhibit very diverse domain organizations. Thus, the unusual right-handed beta-helical fold present in C-CAP appears to support a wide range of biological functions.
Collapse
Affiliation(s)
- Tetyana Dodatko
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Mattila PK, Quintero-Monzon O, Kugler J, Moseley JB, Almo SC, Lappalainen P, Goode BL. A high-affinity interaction with ADP-actin monomers underlies the mechanism and in vivo function of Srv2/cyclase-associated protein. Mol Biol Cell 2004; 15:5158-71. [PMID: 15356265 PMCID: PMC524793 DOI: 10.1091/mbc.e04-06-0444] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Cyclase-associated protein (CAP), also called Srv2 in Saccharomyces cerevisiae, is a conserved actin monomer-binding protein that promotes cofilin-dependent actin turnover in vitro and in vivo. However, little is known about the mechanism underlying this function. Here, we show that S. cerevisiae CAP binds with strong preference to ADP-G-actin (Kd 0.02 microM) compared with ATP-G-actin (Kd 1.9 microM) and competes directly with cofilin for binding ADP-G-actin. Further, CAP blocks actin monomer addition specifically to barbed ends of filaments, in contrast to profilin, which blocks monomer addition to pointed ends of filaments. The actin-binding domain of CAP is more extensive than previously suggested and includes a recently solved beta-sheet structure in the C-terminus of CAP and adjacent sequences. Using site-directed mutagenesis, we define evolutionarily conserved residues that mediate binding to ADP-G-actin and demonstrate that these activities are required for CAP function in vivo in directing actin organization and polarized cell growth. Together, our data suggest that in vivo CAP competes with cofilin for binding ADP-actin monomers, allows rapid nucleotide exchange to occur on actin, and then because of its 100-fold weaker binding affinity for ATP-actin compared with ADP-actin, allows other cellular factors such as profilin to take the handoff of ATP-actin and facilitate barbed end assembly.
Collapse
Affiliation(s)
- Pieta K Mattila
- Program in Cellular Biotechnology, Institute of Biotechnology, University of Helsinki, Helsinki 00014, Finland
| | | | | | | | | | | | | |
Collapse
|
21
|
Balcer HI, Goodman AL, Rodal AA, Smith E, Kugler J, Heuser JE, Goode BL. Coordinated regulation of actin filament turnover by a high-molecular-weight Srv2/CAP complex, cofilin, profilin, and Aip1. Curr Biol 2004; 13:2159-69. [PMID: 14680631 DOI: 10.1016/j.cub.2003.11.051] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Dynamic remodeling of the actin cytoskeleton requires rapid turnover of actin filaments, which is regulated in part by the actin filament severing/depolymerization factor cofilin/ADF. Two factors that cooperate with cofilin are Srv2/CAP and Aip1. Human CAP enhances cofilin-mediated actin turnover in vitro, but its biophysical properties have not been defined, and there has been no in vivo evidence reported for its role in turnover. Xenopus Aip1 forms a cofilin-dependent cap at filament barbed ends. It has been unclear how these diverse activities are coordinated in vivo. RESULTS Purified native yeast Srv2/CAP forms a high molecular weight structure comprised solely of actin and Srv2. The complex is linked to actin filaments via the SH3 domain of Abp1. Srv2 complex catalytically accelerates cofilin-dependent actin turnover by releasing cofilin from ADP-actin monomers and enhances the ability of profilin to stimulate nucleotide exchange on ADP-actin. Yeast Aip1 forms a cofilin-dependent filament barbed end cap, disrupted by the cof1-19 mutant. Genetic analyses show that specific combinations of activities mediated by cofilin, Srv2, Aip1, and capping protein are required in vivo. CONCLUSIONS We define two genetically and biochemically separable functions for cofilin in actin turnover. One is formation of an Aip1-cofilin cap at filament barbed ends. The other is cofilin-mediated severing/depolymerization of filaments, accelerated indirectly by Srv2 complex. We show that the Srv2 complex is a large multimeric structure and functions as an intermediate in actin monomer processing, converting cofilin bound ADP-actin monomers to profilin bound ATP-actin monomers and recycling cofilin for new rounds of filament depolymerization.
Collapse
Affiliation(s)
- Heath I Balcer
- Department of Biology and Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454, USA
| | | | | | | | | | | | | |
Collapse
|
22
|
Wills Z, Emerson M, Rusch J, Bikoff J, Baum B, Perrimon N, Van Vactor D. A Drosophila homolog of cyclase-associated proteins collaborates with the Abl tyrosine kinase to control midline axon pathfinding. Neuron 2002; 36:611-22. [PMID: 12441051 DOI: 10.1016/s0896-6273(02)01022-x] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
We demonstrate that Drosophila capulet (capt), a homolog of the adenylyl cyclase-associated protein that binds and regulates actin in yeast, associates with Abl in Drosophila cells, suggesting a functional relationship in vivo. We find a robust and specific genetic interaction between capt and Abl at the midline choice point where the growth cone repellent Slit functions to restrict axon crossing. Genetic interactions between capt and slit support a model where Capt and Abl collaborate as part of the repellent response. Further support for this model is provided by genetic interactions that both capt and Abl display with multiple members of the Roundabout receptor family. These studies identify Capulet as part of an emerging pathway linking guidance signals to regulation of cytoskeletal dynamics and suggest that the Abl pathway mediates signals downstream of multiple Roundabout receptors.
Collapse
Affiliation(s)
- Zachary Wills
- Department of Cell Biology and Program in Neuroscience, Harvard Medical School, Boston, MA 02115, USA
| | | | | | | | | | | | | |
Collapse
|
23
|
Gurunathan S, Marash M, Weinberger A, Gerst JE. t-SNARE phosphorylation regulates endocytosis in yeast. Mol Biol Cell 2002; 13:1594-607. [PMID: 12006655 PMCID: PMC111129 DOI: 10.1091/mbc.01-11-0541] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Earlier we demonstrated that activation of a ceramide-activated protein phosphatase (CAPP) conferred normal growth and secretion to yeast lacking their complement of exocytic v-SNAREs (Snc1,2) or bearing a temperature-sensitive mutation in an exocytic t-SNARE (Sso2). CAPP activation led to Sso dephosphorylation and enhanced the assembly of t-SNAREs into functional complexes. Thus, exocytosis in yeast is modulated by t-SNARE phosphorylation. Here, we show that endocytic defects in cells lacking the v- and t-SNAREs involved in endocytosis are also rescued by CAPP activation. Yeast lacking the Tlg1 or Tlg2 t-SNAREs, the Snc v-SNAREs, or both, undergo endocytosis after phosphatase activation. CAPP activation correlated with restored uptake of FM4-64 to the vacuole, the uptake and degradation of the Ste2 receptor after mating factor treatment, and the dephosphorylation and assembly of Tlg1,2 into SNARE complexes. Activation of the phosphatase by treatment with C(2)-ceramide, VBM/ELO gene inactivation, or by the overexpression of SIT4 was sufficient to confer rescue. Finally, we found that mutation of single PKA sites in Tlg1 (Ser31 to Ala31) or Tlg2 (Ser90 to Ala90) was sufficient to restore endocytosis, but not exocytosis, to snc cells. These results suggest that endocytosis is also modulated by t-SNARE phosphorylation in vivo.
Collapse
|
24
|
Hubberstey AV, Mottillo EP. Cyclase-associated proteins: CAPacity for linking signal transduction and actin polymerization. FASEB J 2002; 16:487-99. [PMID: 11919151 DOI: 10.1096/fj.01-0659rev] [Citation(s) in RCA: 159] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Many extracellular signals elicit changes in the actin cytoskeleton, which are mediated through an array of signaling proteins and pathways. One family of proteins that plays a role in regulating actin remodeling in response to cellular signals are the cyclase-associated proteins (CAPs). CAPs are highly conserved monomeric actin binding proteins present in a wide range of organisms including yeast, fly, plants, and mammals. The original CAP was isolated as a component of the Saccharomyces cerevisiae adenylyl cyclase complex that serves as an effector of Ras during nutritional signaling. CAPs are multifunctional molecules that contain domains involved in actin binding, adenylyl cyclase association in yeast, SH3 binding, and oligomerization. Genetic studies in yeast have implicated CAPs in vesicle trafficking and endocytosis. CAPs play a developmental role in multicellular organisms, and studies of Drosophila have illuminated the importance of the actin cytoskeleton during eye development and in establishing oocyte polarity. This review will highlight the critical structural and functional domains of CAPs, describe recent studies that have implied important roles for these proteins in linking cell signaling with actin polymerization, and highlight their roles in vesicle trafficking and development.
Collapse
Affiliation(s)
- Andrew V Hubberstey
- Department of Biological Sciences, University of Windsor, Windsor, Ontario, Canada.
| | | |
Collapse
|
25
|
Abstract
The actin cytoskeleton plays a central role in many cell biological processes. The structure and dynamics of the actin cytoskeleton are regulated by numerous actin-binding proteins that usually contain one of the few known actin-binding motifs. WH2 domain (WASP homology domain-2) is a approximately 35 residue actin monomer-binding motif, that is found in many different regulators of the actin cytoskeleton, including the beta-thymosins, ciboulot, WASP (Wiskott Aldrich syndrome protein), verprolin/WIP (WASP-interacting protein), Srv2/CAP (adenylyl cyclase-associated protein) and several uncharacterized proteins. The most highly conserved residues in the WH2 domain are important in beta-thymosin's interactions with actin monomers, suggesting that all WH2 domains may interact with actin monomers through similar interfaces. Our sequence database searches did not reveal any WH2 domain-containing proteins in plants. However, we found three classes of these proteins: WASP, Srv2/CAP and verprolin/WIP in yeast and animals. This suggests that the WH2 domain is an ancient actin monomer-binding motif that existed before the divergence of fungal and animal lineages.
Collapse
Affiliation(s)
- Eija Paunola
- Program in Cellular Biotechnology, Institute of Biotechnology, Viikki Biocenter, P.O. Box 56, University of Helsinki, 00014 Helsinki, Finland
| | | | | |
Collapse
|
26
|
Ponting CP, Mott R, Bork P, Copley RR. Novel protein domains and repeats in Drosophila melanogaster: insights into structure, function, and evolution. Genome Res 2001; 11:1996-2008. [PMID: 11731489 DOI: 10.1101/gr.198701] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Sequence database searching methods such as BLAST, are invaluable for predicting molecular function on the basis of sequence similarities among single regions of proteins. Searches of whole databases however, are not optimized to detect multiple homologous regions within a single polypeptide. Here we have used the prospero algorithm to perform self-comparisons of all predicted Drosophila melanogaster gene products. Predicted repeats, and their homologs from all species, were analyzed further to detect hitherto unappreciated evolutionary relationships. Results included the identification of novel tandem repeats in the human X-linked retinitis pigmentosa type-2 gene product, repeated segments in cystinosin, associated with a defect in cystine transport, and 'nested' homologous domains in dysferlin, whose gene is mutated in limb girdle muscular dystrophy. Novel signaling domain families were found that may regulate the microtubule-based cytoskeleton and ubiquitin-mediated proteolysis, respectively. Two families of glycosyl hydrolases were shown to contain internal repetitions that hint at their evolution via a piecemeal, modular approach. In addition, three examples of fruit fly genes were detected with tandem exons that appear to have arisen via internal duplication. These findings demonstrate how completely sequenced genomes can be exploited to further understand the relationships between molecular structure, function, and evolution.
Collapse
MESH Headings
- Amino Acid Sequence/genetics
- Amino Acid Transport Systems, Neutral
- Animals
- Antigens, Differentiation, B-Lymphocyte/chemistry
- Antigens, Differentiation, B-Lymphocyte/genetics
- Antigens, Differentiation, B-Lymphocyte/physiology
- Aspartate-tRNA Ligase/chemistry
- Aspartate-tRNA Ligase/genetics
- Aspartate-tRNA Ligase/physiology
- Cystinosis/genetics
- Drosophila Proteins/chemistry
- Drosophila Proteins/genetics
- Drosophila Proteins/physiology
- Drosophila melanogaster/chemistry
- Drosophila melanogaster/enzymology
- Drosophila melanogaster/genetics
- Evolution, Molecular
- Exons/genetics
- Eye Proteins
- GTP-Binding Proteins
- Gene Duplication
- Glycoproteins
- Glycoside Hydrolases/chemistry
- Glycoside Hydrolases/genetics
- Glycoside Hydrolases/physiology
- Histocompatibility Antigens Class II/chemistry
- Histocompatibility Antigens Class II/genetics
- Histocompatibility Antigens Class II/physiology
- Humans
- Insect Proteins/chemistry
- Insect Proteins/genetics
- Insect Proteins/physiology
- Intracellular Signaling Peptides and Proteins
- Membrane Proteins/chemistry
- Membrane Proteins/genetics
- Membrane Proteins/physiology
- Membrane Transport Proteins
- Molecular Sequence Data
- Muscular Dystrophies/genetics
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Proteins/chemistry
- Proteins/genetics
- Proteins/physiology
- Repetitive Sequences, Amino Acid
- Retinitis Pigmentosa/genetics
- Signal Transduction/genetics
- Species Specificity
- Tandem Repeat Sequences
Collapse
Affiliation(s)
- C P Ponting
- MRC Functional Genetics Unit, Department of Human Anatomy and Genetics, University of Oxford, Oxford OX1 3QX, UK.
| | | | | | | |
Collapse
|
27
|
Becker B, Vogt T, Landthaler M, Stolz W. Detection of differentially regulated genes in keratinocytes by cDNA array hybridization: Hsp27 and other novel players in response to artificial ultraviolet radiation. J Invest Dermatol 2001; 116:983-8. [PMID: 11407992 DOI: 10.1046/j.1523-1747.2001.01347.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
cDNA array technology was used to identify novel genes participating in the ultraviolet response of cultured human keratinocytes. cDNA arrays representing more than 50,000 different cDNA clones were hybridized with complex probes generated by SMART-polymerase chain reaction amplification of 150 ng of total RNA extracted 24 h after ultraviolet irradiation. Fifty-one clones with differential hybridization signals were detected, representing 19 different sequences; 10 known genes (seven ultraviolet induced, three ultraviolet suppressed) and further nine expressed sequence tags of unknown genes. In seven of 10 genes the data from cDNA arrays probed with SMART-cDNA could be confirmed by northern blot analysis. The 27 kDa heat shock protein mRNA was induced. Keratins 6 and 17, markers for the hyperproliferative status of keratinocytes, were among the ultraviolet suppressed genes. The change of expression profile of keratins indicates a differentiation towards a phenotype of keratinocytes present in the suprabasal layers of the epidermis. These mechanisms may contribute to the ultraviolet protective function of the epidermis and to the anti-proliferative action of ultraviolet in the therapy of psoriasis. We also detected an induction of adenylyl cyclase associated protein and the suppression of G(s)alpha (a stimulating subunit of the trimeric membrane bound GTPase).
Collapse
Affiliation(s)
- B Becker
- Department of Dermatology, University of Regensburg, Regensburg, Germany
| | | | | | | |
Collapse
|
28
|
Bahn YS, Sundstrom P. CAP1, an adenylate cyclase-associated protein gene, regulates bud-hypha transitions, filamentous growth, and cyclic AMP levels and is required for virulence of Candida albicans. J Bacteriol 2001; 183:3211-23. [PMID: 11325951 PMCID: PMC95223 DOI: 10.1128/jb.183.10.3211-3223.2001] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In response to a wide variety of environmental stimuli, the opportunistic fungal pathogen Candida albicans exits the budding cycle, producing germ tubes and hyphae concomitant with expression of virulence genes, such as that encoding hyphal wall protein 1 (HWP1). Biochemical studies implicate cyclic AMP (cAMP) increases in promoting bud-hypha transitions, but genetic evidence relating genes that control cAMP levels to bud-hypha transitions has not been reported. Adenylate cyclase-associated proteins (CAPs) of nonpathogenic fungi interact with Ras and adenylate cyclase to increase cAMP levels under specific environmental conditions. To initiate studies on the relationship between cAMP signaling and bud-hypha transitions in C. albicans, we identified, cloned, characterized, and disrupted the C. albicans CAP1 gene. C. albicans strains with inactivated CAP1 budded in conditions that led to germ tube formation in isogenic strains with CAP1. The addition of 10 mM cAMP and dibutyryl cAMP promoted bud-hypha transitions and filamentous growth in the cap1/cap1 mutant in liquid and solid media, respectively, showing clearly that cAMP promotes hypha formation in C. albicans. Increases in cytoplasmic cAMP preceding germ tube emergence in strains having CAP1 were markedly diminished in the budding cap1/cap1 mutant. C. albicans strains with deletions of both alleles of CAP1 were avirulent in a mouse model of systemic candidiasis. The avirulence of a germ tube-deficient cap1/cap1 mutant coupled with the role of Cap1 in regulating cAMP levels shows that the Cap1-mediated cAMP signaling pathway is required for bud-hypha transitions, filamentous growth, and the pathogenesis of candidiasis.
Collapse
Affiliation(s)
- Y S Bahn
- Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University College of Medicine and Public Health, 333 W. 10th Ave., Columbus, OH 43210-1239, USA
| | | |
Collapse
|
29
|
Abstract
Genetic and biochemical studies in yeast and animal cells have led to the identification of many components required for endocytosis. In this review, we summarize our understanding of the endocytic machinery with an emphasis on the proteins regulating the internalization step of endocytosis and endosome fusion. Even though the overall endocytic machinery appears to be conserved between yeast and animals, clear differences exist. We also discuss the roles of phosphoinositides, sterols, and sphingolipid precursors in endocytosis, because in addition to proteins, these lipids have emerged as important determinants in the spatial and most likely temporal specificity of endocytic membrane trafficking events.
Collapse
Affiliation(s)
- K D'Hondt
- Biozentrum-University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
| | | | | |
Collapse
|
30
|
Ishimaru Y, Yasuoka A, Asano-Miyoshi M, Abe K, Emori Y. An actin-binding protein, CAP, is expressed in a subset of rat taste bud cells. Neuroreport 2001; 12:233-5. [PMID: 11209926 DOI: 10.1097/00001756-200102120-00011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Single cell cDNA libraries were constructed from taste bud cells of rat circumvallate papillae. Using three steps of screening, including differential hybridization, sequence analyses and in situ hybridization, a clone encoding a rat homolog of yeast adenylyl cyclase-associated protein (CAP) was identified to be highly expressed in a subset of taste bud cells.
Collapse
Affiliation(s)
- Y Ishimaru
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Japan
| | | | | | | | | |
Collapse
|
31
|
Gurunathan S, Chapman-Shimshoni D, Trajkovic S, Gerst JE. Yeast exocytic v-SNAREs confer endocytosis. Mol Biol Cell 2000; 11:3629-43. [PMID: 11029060 PMCID: PMC15020 DOI: 10.1091/mbc.11.10.3629] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
In yeast, homologues of the synaptobrevin/VAMP family of v-SNAREs (Snc1 and Snc2) confer the docking and fusion of secretory vesicles at the cell surface. As no v-SNARE has been shown to confer endocytosis, we examined whether yeast lacking the SNC genes, or possessing a temperature-sensitive allele of SNC1 (SNC1(ala43)), are deficient in the endocytic uptake of components from the cell surface. We found that both SNC and temperature-shifted SNC1(ala43) yeast are deficient in their ability to deliver the soluble dye FM4-64 to the vacuole. Under conditions in which vesicles accumulate, FM4-64 stained primarily the cytoplasm as well as fragmented vacuoles. In addition, alpha-factor-stimulated endocytosis of the alpha-factor receptor, Ste2, was fully blocked, as evidenced using a Ste2-green fluorescent protein fusion protein as well as metabolic labeling studies. This suggests a direct role for Snc v-SNAREs in the retrieval of membrane proteins from the cell surface. Moreover, this idea is supported by genetic and physical data that demonstrate functional interactions with t-SNAREs that confer endosomal transport (e.g., Tlg1,2). Notably, Snc1(ala43) was found to be nonfunctional in cells lacking Tlg1 or Tlg2. Thus, we propose that synaptobrevin/VAMP family members are engaged in anterograde and retrograde protein sorting steps between the Golgi and the plasma membrane.
Collapse
Affiliation(s)
- S Gurunathan
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | | | | | | |
Collapse
|
32
|
Baum B, Li W, Perrimon N. A cyclase-associated protein regulates actin and cell polarity during Drosophila oogenesis and in yeast. Curr Biol 2000; 10:964-73. [PMID: 10985383 DOI: 10.1016/s0960-9822(00)00640-0] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
BACKGROUND A polarised cytoskeleton is required to pattern cellular space, and for many aspects of cell behaviour. While the mechanisms ordering the actin cytoskeleton have been extensively studied in yeast, little is known about the analogous processes in other organisms. We have used Drosophila oogenesis as a model genetic system in which to investigate control of cytoskeletal organisation and cell polarity in multicellular eukaryotes. RESULTS In a screen to identify genes required for Drosophila oocyte polarity, we isolated a Drosophila homologue of the yeast cyclase-associated protein, CAP. Here we show that CAP preferentially accumulates in the oocyte, where it inhibits actin polymerisation. CAP also has a role in oocyte polarity, as cap mutants fail to establish the proper, asymmetric distribution of mRNA determinants within the oocyte. Similarly in yeast, loss of CAP causes analogous polarity defects, altering the distribution of actin filaments and mRNA determinants. CONCLUSIONS This study identifies CAP as a new effector of actin dynamics in Drosophila. As CAP controls the spatial distribution of actin filaments and mRNA determinants in both yeast and Drosophila, we conclude that CAP has an evolutionarily conserved function in the genesis of eukaryotic cell polarity.
Collapse
Affiliation(s)
- B Baum
- Department of Genetics, Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts 02215, USA
| | | | | |
Collapse
|
33
|
Benlali A, Draskovic I, Hazelett DJ, Treisman JE. act up controls actin polymerization to alter cell shape and restrict Hedgehog signaling in the Drosophila eye disc. Cell 2000; 101:271-81. [PMID: 10847682 DOI: 10.1016/s0092-8674(00)80837-5] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Cells in the morphogenetic furrow of the Drosophila eye disc undergo a striking shape change immediately prior to their neuronal differentiation. We have isolated mutations in a novel gene, act up (acu), that is required for this shape change. acu encodes a homolog of yeast cyclase-associated protein, which sequesters monomeric actin; we show that acu is required to prevent actin filament polymerization in the eye disc. In contrast, profilin promotes actin filament polymerization, acting epistatically to acu. However, both acu and profilin are required to prevent premature Hedgehog-induced photoreceptor differentiation ahead of the morphogenetic furrow. These findings suggest that dynamic changes in actin filaments alter cell shape to control the movement of signals that coordinate a wave of differentiation.
Collapse
Affiliation(s)
- A Benlali
- Skirball Institute of Biomolecular Medicine and Department of Cell Biology, New York University School of Medicine, New York 10016, USA
| | | | | | | |
Collapse
|
34
|
Freeman NL, Field J. Mammalian homolog of the yeast cyclase associated protein, CAP/Srv2p, regulates actin filament assembly. CELL MOTILITY AND THE CYTOSKELETON 2000; 45:106-20. [PMID: 10658207 DOI: 10.1002/(sici)1097-0169(200002)45:2<106::aid-cm3>3.0.co;2-3] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Control of cell shape and motility requires rearrangements of the actin cytoskeleton. One cytoskeletal protein that may regulate actin dynamics is CAP (cyclase associated protein; CAP/Srv2p; ASP-56). CAP was first isolated from yeast as an adenylyl cyclase associated protein required for RAS regulation of cAMP signaling. In addition, CAP also regulates the actin cytoskeleton primarily through an actin monomer binding activity. CAP homologs are found in many eukaryotes, including mammals where they also bind actin, but little is known about their biological function. We, therefore, designed experiments to address CAP1 regulation of the actin cytoskeleton. CAP1 localized to membrane ruffles and actin stress fibers in fixed cells of various types. To address localization in living cells, we constructed GFP-CAP1 fusion proteins and found that fusion proteins lacking the actin-binding region localized like the wild type protein. We also performed microinjection studies with affinity-purified anti-CAP1 antibodies in Swiss 3T3 fibroblasts and found that the antibodies attenuated serum stimulation of stress fibers. Finally, CAP1 purified from platelets through a monoclonal antibody affinity purification step stimulated the formation of stress fiber-like filaments when it was microinjected into serum-starved Swiss 3T3 cells. Taken together, these data suggest that CAP1 promotes assembly of the actin cytoskeleton.
Collapse
Affiliation(s)
- N L Freeman
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | | |
Collapse
|
35
|
Abstract
ParB is one of two P1-encoded proteins that are required for active partition of the P1 prophage in Escherichia coli. To probe the native domain structure of ParB, we performed limited proteolytic digestions of full-length ParB, as well as of several N-terminal and C-terminal deletion fragments of ParB. The C-terminal 140 amino acids of ParB form a very trypsin-resistant domain. In contrast, the N terminus is more susceptible to proteolysis, suggesting that it forms a less stably folded domain or domains. Because native ParB is a dimer in solution, we analyzed the ability of ParB fragments to dimerize, using both the yeast two-hybrid system and in vitro chemical cross-linking of purified proteins. These studies revealed that the C-terminal 59 amino acids of ParB, a region within the protease-resistant domain, are sufficient for dimerization. Cross-linking and yeast two-hybrid experiments also revealed the presence of a second self-association domain within the N-terminal half of ParB. The cross-linking data also suggest that the C terminus is inhibitory to multimerization through the N-terminal domain in vitro. We propose that the two multimerization domains play distinct roles in partition complex formation.
Collapse
Affiliation(s)
- J A Surtees
- Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | | |
Collapse
|
36
|
Yu J, Wang C, Palmieri SJ, Haarer BK, Field J. A cytoskeletal localizing domain in the cyclase-associated protein, CAP/Srv2p, regulates access to a distant SH3-binding site. J Biol Chem 1999; 274:19985-91. [PMID: 10391948 DOI: 10.1074/jbc.274.28.19985] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the yeast, Saccharomyces cerevisiae, adenylyl cyclase consists of a 200-kDa catalytic subunit (CYR1) and a 70-kDa subunit (CAP/SRV2). CAP/Srv2p assists the small G protein Ras to activate adenylyl cyclase. CAP also regulates the cytoskeleton through an actin sequestering activity and is directed to cortical actin patches by a proline-rich SH3-binding site (P2). In this report we analyze the role of the actin cytoskeleton in Ras/cAMP signaling. Two alleles of CAP, L16P(Srv2) and R19T (SupC), first isolated in genetic screens for mutants that attenuate cAMP levels, reduced adenylyl cyclase binding, and cortical actin patch localization. A third mutation, L27F, also failed to localize but showed no loss of either cAMP signaling or adenylyl cyclase binding. However, all three N-terminal mutations reduced CAP-CAP multimer formation and SH3 domain binding, although the SH3-binding site is about 350 amino acids away. Finally, disruption of the actin cytoskeleton with latrunculin-A did not affect the cAMP phenotypes of the hyperactive Ras2(Val19) allele. These data identify a novel region of CAP that controls access to the SH3-binding site and demonstrate that cytoskeletal localization of CAP or an intact cytoskeleton per se is not necessary for cAMP signaling.
Collapse
Affiliation(s)
- J Yu
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
| | | | | | | | | |
Collapse
|
37
|
Lustgarten V, Gerst JE. Yeast VSM1 encodes a v-SNARE binding protein that may act as a negative regulator of constitutive exocytosis. Mol Cell Biol 1999; 19:4480-94. [PMID: 10330187 PMCID: PMC104406 DOI: 10.1128/mcb.19.6.4480] [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: 11/20/2022] Open
Abstract
We have screened for proteins that interact with v-SNAREs of the late secretory pathway in the yeast Saccharomyces cerevisiae. A novel protein, designated Vsm1, binds tightly to the Snc2 v-SNARE in the two-hybrid system and can be coimmunoprecipitated with Snc1 or Snc2 from solubilized yeast cell extracts. Disruption of the VSM1 gene results in an increase of proteins secreted into the medium but does not affect the processing or secretion of invertase. In contrast, VSM1 overexpression in cells which bear a temperature-sensitive mutation in the Sec9 t-SNARE (sec9-4 cells) results in the accumulation of non-invertase-containing low-density secretory vesicles, inhibits cell growth and the secretion of proteins into the medium, and blocks rescue of the temperature-sensitive phenotype by SNC1 overexpression. Yet, VSM1 overexpression does not affect yeast bearing a sec9-7 allele which, in contrast to sec9-4, encodes a t-SNARE protein capable of forming a stable SNARE complex in vitro at restrictive temperatures. On the basis of these results, we propose that Vsm1 is a novel v-SNARE-interacting protein that appears to act as negative regulator of constitutive exocytosis. Moreover, this regulation appears specific to one of two parallel exocytic paths which are operant in yeast cells.
Collapse
Affiliation(s)
- V Lustgarten
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | | |
Collapse
|
38
|
David D, Sundarababu S, Gerst JE. Involvement of long chain fatty acid elongation in the trafficking of secretory vesicles in yeast. J Biophys Biochem Cytol 1998; 143:1167-82. [PMID: 9832547 PMCID: PMC2133077 DOI: 10.1083/jcb.143.5.1167] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Members of the synaptobrevin/VAMP family of v-SNAREs are thought to be essential for vesicle docking and exocytosis in both lower and higher eukaryotes. Here, we describe yeast mutants that appear to bypass the known v-SNARE requirement in secretion. Recessive mutations in either VBM1 or VBM2, which encode related ER-localized membrane proteins, allow yeast to grow normally and secrete in the absence of Snc v-SNAREs. These mutants show selective alterations in protein transport, resulting in the differential trafficking and secretion of certain protein cargo. Yet, processing of the vacuolar marker, carboxypeptidase Y, and the secreted protein, invertase, appear normal in these mutants indicating that general protein trafficking early in the pathway is unaffected. Interestingly, VBM1 and VBM2 are allelic to ELO3 and ELO2, two genes that have been shown recently to mediate the elongation of very long chain fatty acids and subsequent ceramide and inositol sphingolipid synthesis. Thus, the v-SNARE requirement in constitutive exocytosis is abrogated by mutations in early components of the secretory pathway that act at the level of lipid synthesis to affect the ability of secretory vesicles to sort and deliver protein cargo.
Collapse
Affiliation(s)
- D David
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | | | | |
Collapse
|
39
|
Nishida Y, Shima F, Sen H, Tanaka Y, Yanagihara C, Yamawaki-Kataoka Y, Kariya K, Kataoka T. Coiled-coil interaction of N-terminal 36 residues of cyclase-associated protein with adenylyl cyclase is sufficient for its function in Saccharomyces cerevisiae ras pathway. J Biol Chem 1998; 273:28019-24. [PMID: 9774417 DOI: 10.1074/jbc.273.43.28019] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the budding yeast Saccharomyces cerevisiae, association with the 70-kDa cyclase-associated protein (CAP) is required for proper response of adenylyl cyclase to Ras proteins. We show here that a small segment comprising the N-terminal 36 amino acid residues of CAP is sufficient for association with adenylyl cyclase as well as for its function in the Ras-adenylyl cyclase pathway as assayed by the ability to confer RAS2(Val-19)-dependent heat shock sensitivity to yeast cells. The CAP-binding site of adenylyl cyclase was mapped to a segment of 119 amino acid residues near its C terminus. Both of these regions contained tandem repetitions of a heptad motif alphaXXalphaXXX (where alpha represents a hydrophobic amino acid and X represents any amino acid), suggesting a coiled-coil interaction. When mutants of CAP defective in associating with adenylyl cyclase were isolated by screening of a pool of randomly mutagenized CAP, they were found to carry substitution mutations in one of the key hydrophobic residues in the heptad repeats. Furthermore, mutations of the key hydrophobic residues in the heptad repeats of adenylyl cyclase also resulted in loss of association with CAP. These results indicate the coiled-coil mechanism as a basis of the CAP-adenylyl cyclase interaction.
Collapse
Affiliation(s)
- Y Nishida
- Department of Physiology II, Kobe University School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
| | | | | | | | | | | | | | | |
Collapse
|
40
|
Zhou GL, Miyazaki Y, Nakagawa T, Tanaka K, Shishido K, Matsuda H, Kawamukai M. Identification of a CAP (adenylyl-cyclase-associated protein) homologous gene in Lentinus edodes and its functional complementation of yeast CAP mutants. MICROBIOLOGY (READING, ENGLAND) 1998; 144 ( Pt 4):1085-1093. [PMID: 9579081 DOI: 10.1099/00221287-144-4-1085] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The adenylyl-cyclase-associated protein, CAP, was originally identified in yeasts as a protein that functions in both signal transduction and cytoskeletal organization. This paper reports the identification of a cDNA and genomic DNA that encodes a CAP homologue from the mushroom Lentinus edodes. The L. edodes cap gene contains eight introns and an ORF encoding a 518 amino acid protein. The L. edodes CAP is 35.5% and 40.9% identical at the amino acid level with Saccharomyces cerevisiae CAP and Schizosaccharomyces pombe CAP, respectively. The C-terminal domain shows greater homology (39-46% identity) with yeast CAPs than does the N-terminal domain (27-35% identity). Southern blotting and Northern blotting results suggest that L. edodes cap is a single-copy gene and uniformly expressed. Expression of the L. edodes CAP in both Schiz. pombe and Sacch. cerevisiae complemented defects associated with the loss of the C-terminal domain function of the endogenous CAP. By using a yeast two-hybrid assay, an interaction was demonstrated between the L. edodes CAP and Schiz. pombe actin. This result and the functional complementation test indicate that CAP from L. edodes has a conserved C-terminal domain function.
Collapse
Affiliation(s)
- Guo-Lei Zhou
- 1 Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, Matsue 690, Japan
| | - Yasumasa Miyazaki
- 2 Department of Life Science, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226, Japan
| | - Tsuyoshi Nakagawa
- 3 Research Institute of Molecular Genetics, Shimane University, Matsue 690, Japan
| | - Katsunori Tanaka
- 1 Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, Matsue 690, Japan
| | - Kazuo Shishido
- 2 Department of Life Science, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226, Japan
| | - Hideyuki Matsuda
- 1 Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, Matsue 690, Japan
| | - Makoto Kawamukai
- 1 Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, Matsue 690, Japan
| |
Collapse
|
41
|
Camus C, Geymonat M, Garreau H, Baudet-Nessler S, Jacquet M. Dimerization of Cdc25p, the guanine-nucleotide exchange factor for Ras from Saccharomyces cerevisiae, and its interaction with Sdc25p. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 247:703-8. [PMID: 9266716 DOI: 10.1111/j.1432-1033.1997.00703.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The oligomerization state of Cdc25p, the guanine nucleotide exchange factor for ras from yeast, was analyzed using different complementary approaches. The two-hybrid system showed that the C-terminal part of Cdc25p (Cdc25-Ct) can interact with itself but also with Sdc25p-Ct, the corresponding part of Sdc25p, the other guanine exchange factor from yeast. The homotropic interaction of Cdc25p-Ct has been confirmed in yeast using immunoprecipitation experiments with epitope-tagged and beta-galactosidase-fused polypeptides. No other component was required for this interaction, since dimerization was shown to occur with material synthesized in vitro. The size of Cdc25-Ct produced in Escherichia coli has been directly measured on gel filtration columns and corresponds to a dimer. The dimerization domain is localized in the same part of the molecule as the catalytic domain and the portion responsible for membrane localization. The biological relevance of dimerization is still an open question, however by allowing heterodimerization with Sdc25p it could permit a more complex combinatorial regulation of ras in yeast.
Collapse
Affiliation(s)
- C Camus
- Laboratoire Information Génétique et Développement, Institut de Génétique et Microbiologie, URA CNRS 2225, Université Paris-Sud, France
| | | | | | | | | |
Collapse
|
42
|
Gerst JE. Conserved alpha-helical segments on yeast homologs of the synaptobrevin/VAMP family of v-SNAREs mediate exocytic function. J Biol Chem 1997; 272:16591-8. [PMID: 9195971 DOI: 10.1074/jbc.272.26.16591] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
We are studying yeast homologs of the synaptobrevin/VAMP family of vesicle-associated membrane proteins, which act as vesicular compartment-soluble N-ethylmaleimide-sensitive factor attachment protein receptors (v-SNAREs) in cells having a capacity for stimulus-coupled secretion, as well as in other cell types. The yeast homologs, Snc1 and Snc2, localize to secretory vesicles and are required for normal bulk secretion in Saccharomyces cerevisiae. Here we have used Snc deletion mutants and chimeric Snc-VAMP proteins to demonstrate that these v-SNAREs can be dissected into regions that are either indispensable or dispensable for exocytic function in vivo. We have found that a region encompassing two predicted amphipathic alpha-helices (helix 1 and helix 2) (residues 32-85), which are thought to form coiled-coil structures, is essential for conferring exocytosis in yeast. Deletions in either the helix 1 or helix 2 segments result in a complete loss in the ability of the protein to confer secretion competence to snc cells and to interact genetically with components of the proposed fusion complex: the Sec9 and Sso2 t-SNAREs and the Sec17 alpha-SNAP homolog. In contrast, deletions in either the variable (residues 2-27) or putative intravesicular (residues 115-117) regions have no deleterious effect upon v-SNARE function. This makes it unlikely that sequences in either the amino or carboxyl terminus act in an exocytic capacity. Along with additional studies utilizing chimeric Snc-VAMP proteins, we suggest that although the Snc and synaptobrevin/VAMP proteins have evolved to mediate vastly different exocytic programs, their structural requirements and actions have remained remarkably well-conserved in evolution.
Collapse
Affiliation(s)
- J E Gerst
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
| |
Collapse
|
43
|
Finger FP, Novick P. Sec3p is involved in secretion and morphogenesis in Saccharomyces cerevisiae. Mol Biol Cell 1997; 8:647-62. [PMID: 9247645 PMCID: PMC276116 DOI: 10.1091/mbc.8.4.647] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Two new temperature-sensitive alleles of SEC3, 1 of 10 late-acting SEC genes required for targeting or fusion of post-Golgi secretory vesicles to the plasma membrane in Saccharomyces cerevisiae, were isolated in a screen for temperature-sensitive secretory mutants that are synthetically lethal with sec4-8. The new sec3 alleles affect early as well as late stages of secretion. Cloning and sequencing of the SEC3 gene revealed that it is identical to profilin synthetic lethal 1 (PSL1). The SEC3 gene is not essential because cells depleted of Sec3p are viable although slow growing and temperature sensitive. All of the sec3 alleles genetically interact with a profilin mutation, pfy1-111. The SEC3 gene in high copy suppresses pfy1-111 and sec5-24 and causes synthetic growth defects with ypt1, sec8-9, sec10-2, and sec15-1. Actin structure is only perturbed in conditions of chronic loss of Sec3p function, implying that Sec3p does not directly regulate actin. All alleles of sec3 cause bud site selection defects in homozygous diploids, as do sec4-8 and sec9-4. This suggests that SEC gene products are involved in determining the bud site and is consistent with a role for Sec3p in determining the correct site of exocytosis.
Collapse
Affiliation(s)
- F P Finger
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520-8002, USA
| | | |
Collapse
|
44
|
Yanagihara C, Shinkai M, Kariya K, Yamawaki-Kataoka Y, Hu CD, Masuda T, Kataoka T. Association of elongation factor 1 alpha and ribosomal protein L3 with the proline-rich region of yeast adenylyl cyclase-associated protein CAP. Biochem Biophys Res Commun 1997; 232:503-7. [PMID: 9125210 DOI: 10.1006/bbrc.1997.6326] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
CAP is a multifunctional protein; the N-terminal region binds adenylyl cyclase and controls its response to Ras while the C-terminal region is involved in cytoskeletal regulation. In between the two regions, CAP possesses two proline-rich segments, P1 and P2, resembling a consensus sequence for binding SH3 domains. We have identified two yeast proteins with molecular sizes of 48 and 46 kDa associated specifically with P2. Determination of partial protein sequences demonstrated that the 48-kDa and 46-kDa proteins correspond to EF1 alpha and rL3, respectively, neither of which contains any SH3-domain-like sequence. Deletion of P2 from CAP resulted in loss of the activity to bind the two proteins either in vivo or in vitro. Yeast cells whose chromosomal CAP was replaced by the P2-deletion mutant displayed an abnormal phenotype represented by dissociated localizations of CAP and F-actin, which were colocalized in wild-type cells. These results suggest that these associations may have functional significance.
Collapse
Affiliation(s)
- C Yanagihara
- Department of Physiology II, Kobe University School of Medicine, Japan
| | | | | | | | | | | | | |
Collapse
|