1
|
Hummel DR, Hakala M, Toret CP, Kaksonen M. Bsp1, a fungal CPI motif protein, regulates actin filament capping in endocytosis and cytokinesis. Mol Biol Cell 2024; 35:br6. [PMID: 38088874 PMCID: PMC10881157 DOI: 10.1091/mbc.e23-10-0391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 11/28/2023] [Accepted: 12/07/2023] [Indexed: 01/14/2024] Open
Abstract
The capping of barbed filament ends is a fundamental mechanism for actin regulation. Capping protein controls filament growth and actin turnover in cells by binding to the barbed ends of the filaments with high affinity and slow off-rate. The interaction between capping protein and actin is regulated by capping protein interaction (CPI) motif proteins. We identified a novel CPI motif protein, Bsp1, which is involved in cytokinesis and endocytosis in budding yeast. We demonstrate that Bsp1 is an actin binding protein with a high affinity for capping protein via its CPI motif. In cells, Bsp1 regulates capping protein at endocytic sites and is a major recruiter of capping protein to the cytokinetic actin ring. Lastly, we define Bsp1-related proteins as a distinct fungi-specific CPI protein group. Our results suggest that Bsp1 promotes actin filament capping by the capping protein. This study establishes Bsp1 as a new capping protein regulator and promising candidate to regulate actin networks in fungi.
Collapse
Affiliation(s)
- Daniel R. Hummel
- Department of Biochemistry, University of Geneva, 1205 Geneva, Switzerland
| | - Markku Hakala
- Department of Biochemistry, University of Geneva, 1205 Geneva, Switzerland
| | | | - Marko Kaksonen
- Department of Biochemistry, University of Geneva, 1205 Geneva, Switzerland
| |
Collapse
|
2
|
Lamb AK, Fernandez AN, Eadaim A, Johnson K, Di Pietro SM. Mechanism of actin capping protein recruitment and turnover during clathrin-mediated endocytosis. J Cell Biol 2024; 223:e202306154. [PMID: 37966720 PMCID: PMC10651396 DOI: 10.1083/jcb.202306154] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 10/11/2023] [Accepted: 11/01/2023] [Indexed: 11/16/2023] Open
Abstract
Clathrin-mediated endocytosis depends on polymerization of a branched actin network to provide force for membrane invagination. A key regulator in branched actin network formation is actin capping protein (CP), which binds to the barbed end of actin filaments to prevent the addition or loss of actin subunits. CP was thought to stochastically bind actin filaments, but recent evidence shows CP is regulated by a group of proteins containing CP-interacting (CPI) motifs. Importantly, how CPI motif proteins function together to regulate CP is poorly understood. Here, we show Aim21 and Bsp1 work synergistically to recruit CP to the endocytic actin network in budding yeast through their CPI motifs, which also allosterically modulate capping strength. In contrast, twinfilin works downstream of CP recruitment, regulating the turnover of CP through its CPI motif and a non-allosteric mechanism. Collectively, our findings reveal how three CPI motif proteins work together to regulate CP in a stepwise fashion during endocytosis.
Collapse
Affiliation(s)
- Andrew K. Lamb
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA
| | - Andres N. Fernandez
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA
| | - Abdunaser Eadaim
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA
| | - Katelyn Johnson
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA
| | - Santiago M. Di Pietro
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA
| |
Collapse
|
3
|
Lamb AK, Fernandez AN, Peersen OB, Di Pietro SM. The dynein light chain protein Tda2 functions as a dimerization engine to regulate actin capping protein during endocytosis. Mol Biol Cell 2021; 32:1459-1473. [PMID: 34081539 PMCID: PMC8351736 DOI: 10.1091/mbc.e21-01-0032] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Clathrin- and actin-mediated endocytosis is a fundamental process in eukaryotic cells. Previously, we discovered Tda2 as a new yeast dynein light chain (DLC) that works with Aim21 to regulate actin assembly during endocytosis. Here we show Tda2 functions as a dimerization engine bringing two Aim21 molecules together using a novel binding surface different than the canonical DLC ligand binding groove. Point mutations on either protein that diminish the Tda2-Aim21 interaction in vitro cause the same in vivo phenotype as TDA2 deletion showing reduced actin capping protein (CP) recruitment and increased filamentous actin at endocytic sites. Remarkably, chemically induced dimerization of Aim21 rescues the endocytic phenotype of TDA2 deletion. We also uncovered a CP interacting motif in Aim21, expanding its function to a fundamental cellular pathway and showing such motif exists outside mammalian cells. Furthermore, specific disruption of this motif causes the same deficit of actin CP recruitment and increased filamentous actin at endocytic sites as AIM21 deletion. Thus, the data indicate the Tda2-Aim21 complex functions in actin assembly primarily through CP regulation. Collectively, our results provide a mechanistic view of the Tda2-Aim21 complex and its function in actin network regulation at endocytic sites.
Collapse
Affiliation(s)
- Andrew K Lamb
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870
| | - Andres N Fernandez
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870
| | - Olve B Peersen
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870
| | - Santiago M Di Pietro
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870
| |
Collapse
|
4
|
Tolsma TO, Febvre HP, Olson DM, Di Pietro SM. Cargo-mediated recruitment of the endocytic adaptor protein Sla1 in S. cerevisiae. J Cell Sci 2020; 133:jcs247684. [PMID: 32907853 PMCID: PMC7578355 DOI: 10.1242/jcs.247684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Accepted: 08/27/2020] [Indexed: 11/20/2022] Open
Abstract
Endocytosis of plasma membrane proteins is mediated by their interaction with adaptor proteins. Conversely, emerging evidence suggests that adaptor protein recruitment to the plasma membrane may depend on binding to endocytic cargo. To test this idea, we analyzed the yeast adaptor protein Sla1, which binds membrane proteins harboring the endocytic signal NPFxD via the Sla1 SHD1 domain. Consistently, SHD1 domain point mutations that disrupted NPFxD binding caused a proportional reduction in Sla1-GFP recruitment to endocytic sites. Furthermore, simultaneous SHD1 domain point mutation and deletion of the C-terminal LxxQxTG repeat (SR) region linking Sla1 to coat proteins Pan1 and End3 resulted in total loss of Sla1-GFP recruitment to the plasma membrane. These data suggest that multiple interactions are needed for recruitment of Sla1 to the membrane. Interestingly, a Sla1 fragment containing just the third SH3 domain, which binds ubiquitin, and the SHD1 domain displayed broad surface localization, suggesting plasma membrane recruitment is mediated by interaction with both NPFxD-containing and ubiquitylated plasma membrane proteins. Our results also imply that a Sla1 NPF motif adjacent to the SR region might regulate the Sla1-cargo interaction, mechanistically linking Sla1 cargo binding to endocytic site recruitment.
Collapse
Affiliation(s)
- Thomas O Tolsma
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870, USA
| | - Hallie P Febvre
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870, USA
| | - Deanna M Olson
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870, USA
| | - Santiago M Di Pietro
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523-1870, USA
| |
Collapse
|
5
|
Mechanism of platelet α-granule biogenesis: study of cargo transport and the VPS33B-VPS16B complex in a model system. Blood Adv 2020; 3:2617-2626. [PMID: 31501156 DOI: 10.1182/bloodadvances.2018028969] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 07/30/2019] [Indexed: 12/29/2022] Open
Abstract
Platelet α-granules play important roles in platelet function. They contain hundreds of proteins that are synthesized by the megakaryocyte or taken up by endocytosis. The trafficking pathways that mediate platelet α-granule biogenesis are incompletely understood, especially with regard to cargo synthesized by the megakaryocyte. Vacuolar-protein sorting 33B (VPS33B) and VPS16B are essential proteins for α-granule biogenesis, but they are largely uncharacterized. Here, we adapted a powerful method to directly map the pathway followed by newly synthesized cargo proteins to reach α-granules. Using this method, we revealed the recycling endosome as a key intermediate compartment in α-granule biogenesis. We then used CRISPR/Cas9 gene editing to knock out VPS33B in pluripotent stem cell-derived immortalized megakaryocyte cells (imMKCLs). Consistent with the observations in platelets from patients with VPS33B mutation, VPS33B-knockout (KO) imMKCLs have drastically reduced levels of α-granule proteins platelet factor 4, von Willebrand factor, and P-selectin. VPS33B and VPS16B form a distinct and small complex in imMKCLs with the same hydrodynamic radius as the recombinant VPS33B-VPS16B heterodimer purified from bacteria. Mechanistically, the VPS33B-VPS16B complex ensures the correct trafficking of α-granule proteins. VPS33B deficiency results in α-granule cargo degradation in lysosomes. VPS16B steady-state levels are significantly lower in VPS33B-KO imMKCLs, suggesting that VPS16B is destabilized in the absence of its partner. Exogenous expression of green fluorescent protein-VPS33B in VPS33B-KO imMKCLs reconstitutes the complex, which localizes to the recycling endosome, further defining this compartment as a key intermediate in α-granule biogenesis. These results advance our understanding of platelet α-granule biogenesis and open new avenues for the study of these organelles.
Collapse
|
6
|
Miao Y, Tipakornsaowapak T, Zheng L, Mu Y, Lewellyn E. Phospho-regulation of intrinsically disordered proteins for actin assembly and endocytosis. FEBS J 2018; 285:2762-2784. [PMID: 29722136 DOI: 10.1111/febs.14493] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 04/04/2018] [Accepted: 04/26/2018] [Indexed: 12/13/2022]
Abstract
Actin filament assembly contributes to the endocytic pathway pleiotropically, with active roles in clathrin-dependent and clathrin-independent endocytosis as well as subsequent endosomal trafficking. Endocytosis comprises a series of dynamic events, including the initiation of membrane curvature, bud invagination, vesicle abscission and subsequent vesicular transport. The ultimate success of endocytosis requires the coordinated activities of proteins that trigger actin polymerization, recruit actin-binding proteins (ABPs) and organize endocytic proteins (EPs) that promote membrane curvature through molecular crowding or scaffolding mechanisms. A particularly interesting phenomenon is that multiple EPs and ABPs contain a substantial percentage of intrinsically disordered regions (IDRs), which can contribute to protein coacervation and phase separation. In addition, intrinsically disordered proteins (IDPs) frequently contain sites for post-translational modifications (PTMs) such as phosphorylation, and these modifications exhibit a high preference for IDR residues [Groban ES et al. (2006) PLoS Comput Biol 2, e32]. PTMs are implicated in regulating protein function by modulating the protein conformation, protein-protein interactions and the transition between order and disorder states of IDPs. The molecular mechanisms by which IDRs of ABPs and EPs fine-tune actin assembly and endocytosis remain mostly unexplored and elusive. In this review, we analyze protein sequences of budding yeast EPs and ABPs, and discuss the potential underlying mechanisms for regulating endocytosis and actin assembly through the emerging concept of IDR-mediated protein multivalency, coacervation, and phase transition, with an emphasis on the phospho-regulation of IDRs. Finally, we summarize the current understanding of how these mechanisms coordinate actin cytoskeleton assembly and membrane curvature formation during endocytosis in budding yeast.
Collapse
Affiliation(s)
- Yansong Miao
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.,School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore, Singapore
| | | | - Liangzhen Zheng
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Yuguang Mu
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Eric Lewellyn
- Department of Biology, Division of Natural Sciences, St Norbert College, De Pere, WI, USA
| |
Collapse
|
7
|
Tolsma TO, Cuevas LM, Di Pietro SM. The Sla1 adaptor-clathrin interaction regulates coat formation and progression of endocytosis. Traffic 2018. [PMID: 29542219 DOI: 10.1111/tra.12563] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Clathrin-mediated endocytosis is a fundamental transport pathway that depends on numerous protein-protein interactions. Testing the importance of the adaptor protein-clathrin interaction for coat formation and progression of endocytosis in vivo has been difficult due to experimental constrains. Here, we addressed this question using the yeast clathrin adaptor Sla1, which is unique in showing a cargo endocytosis defect upon substitution of 3 amino acids in its clathrin-binding motif (sla1AAA ) that disrupt clathrin binding. Live-cell imaging showed an impaired Sla1-clathrin interaction causes reduced clathrin levels but increased Sla1 levels at endocytic sites. Moreover, the rate of Sla1 recruitment was reduced indicating proper dynamics of both clathrin and Sla1 depend on their interaction. sla1AAA cells showed a delay in progression through the various stages of endocytosis. The Arp2/3-dependent actin polymerization machinery was present for significantly longer time before actin polymerization ensued, revealing a link between coat formation and activation of actin polymerization. Ultimately, in sla1AAA cells a larger than normal actin network was formed, dramatically higher levels of various machinery proteins other than clathrin were recruited, and the membrane profile of endocytic invaginations was longer. Thus, the Sla1-clathrin interaction is important for coat formation, regulation of endocytic progression and membrane bending.
Collapse
Affiliation(s)
- Thomas O Tolsma
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado
| | - Lena M Cuevas
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado
| | - Santiago M Di Pietro
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado
| |
Collapse
|
8
|
Farrell KB, McDonald S, Lamb AK, Worcester C, Peersen OB, Di Pietro SM. Novel function of a dynein light chain in actin assembly during clathrin-mediated endocytosis. J Cell Biol 2017; 216:2565-2580. [PMID: 28706108 PMCID: PMC5551697 DOI: 10.1083/jcb.201604123] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 01/04/2017] [Accepted: 05/12/2017] [Indexed: 11/22/2022] Open
Abstract
Actin-capping protein is a key component of the actin cytoskeleton at sites of clathrin-mediated endocytosis. Farrell et al. show that a newly discovered component of the endocytic machinery belongs to the dynein light chain family and regulates the recruitment of actin-capping protein in a dynein motor–independent manner. Clathrin- and actin-mediated endocytosis is essential in eukaryotic cells. In this study, we demonstrate that Tda2 is a novel protein of the endocytic machinery necessary for normal internalization of native cargo in yeast. Tda2 has not been classified in any protein family. Unexpectedly, solving the crystal structure of Tda2 revealed it belongs to the dynein light chain family. However, Tda2 works independently of the dynein motor complex and microtubules. Tda2 forms a tight complex with the polyproline motif–rich protein Aim21, which interacts physically with the SH3 domain of the Arp2/3 complex regulator Bbc1. The Tda2–Aim21 complex localizes to endocytic sites in a Bbc1- and filamentous actin–dependent manner. Importantly, the Tda2–Aim21 complex interacts directly with and facilitates the recruitment of actin-capping protein, revealing barbed-end filament capping at endocytic sites to be a regulated event. Thus, we have uncovered a new layer of regulation of the actin cytoskeleton by a member of a conserved protein family that has not been previously associated with a function in endocytosis.
Collapse
Affiliation(s)
- Kristen B Farrell
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO
| | - Seth McDonald
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO
| | - Andrew K Lamb
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO
| | - Colette Worcester
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO
| | - Olve B Peersen
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO
| | - Santiago M Di Pietro
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO
| |
Collapse
|
9
|
Tyler JJ, Allwood EG, Ayscough KR. WASP family proteins, more than Arp2/3 activators. Biochem Soc Trans 2016; 44:1339-1345. [PMID: 27911716 PMCID: PMC5095904 DOI: 10.1042/bst20160176] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Revised: 07/14/2016] [Accepted: 07/21/2016] [Indexed: 01/19/2023]
Abstract
Wiskott-Aldrich syndrome protein (WASP) family proteins have been extensively characterized as factors that promote the nucleation of actin through the activation of the protein complex Arp2/3. While yeast mostly have a single member of the family, mammalian cells have at least six different members, often with multiple isoforms. Members of the family are characterized by a common structure. Their N-termini are varied and are considered to confer spatial and temporal regulation of Arp2/3-activating activity, whereas their C-terminal half contains a polyproline-rich region, one or more WASP homology-2 (WH2) actin-binding domains and motifs that bind directly to Arp2/3. Recent studies, however, indicate that the yeast WASP homologue Las17 is able to nucleate actin independently of Arp2/3 through the function of novel G-actin-binding activities in its polyproline region. This allows Las17 to generate the mother filaments that are needed for subsequent Arp2/3 recruitment and activation during the actin polymerization that drives endocytic invagination in yeast. In this review, we consider how motifs within the polyproline region of Las17 support nucleation of actin filaments, and whether similar mechanisms might exist among other family members.
Collapse
Affiliation(s)
- Joe J Tyler
- Department of Biomedical Science, Firth Court, University of Sheffield, Sheffield S10 2TN, U.K
| | - Ellen G Allwood
- Department of Biomedical Science, Firth Court, University of Sheffield, Sheffield S10 2TN, U.K
| | - Kathryn R Ayscough
- Department of Biomedical Science, Firth Court, University of Sheffield, Sheffield S10 2TN, U.K
| |
Collapse
|
10
|
Allwood EG, Tyler JJ, Urbanek AN, Smaczynska-de Rooij II, Ayscough KR. Elucidating Key Motifs Required for Arp2/3-Dependent and Independent Actin Nucleation by Las17/WASP. PLoS One 2016; 11:e0163177. [PMID: 27637067 PMCID: PMC5026357 DOI: 10.1371/journal.pone.0163177] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 09/02/2016] [Indexed: 12/21/2022] Open
Abstract
Actin nucleation is the key rate limiting step in the process of actin polymerization, and tight regulation of this process is critical to ensure actin filaments form only at specific times and at defined regions of the cell. Arp2/3 is a well-characterised protein complex that can promote nucleation of new filaments, though its activity requires additional nucleation promotion factors (NPFs). The best recognized of these factors are the WASP family of proteins that contain binding motifs for both monomeric actin and for Arp2/3. Previously we demonstrated that the yeast WASP homologue, Las17, in addition to activating Arp2/3 can also nucleate actin filaments de novo, independently of Arp2/3. This activity is dependent on its polyproline rich region. Through biochemical and in vivo analysis we have now identified key motifs within the polyproline region that are required for nucleation and elongation of actin filaments, and have addressed the role of the WH2 domain in the context of actin nucleation without Arp2/3. We have also demonstrated that full length Las17 is able to bind liposomes giving rise to the possibility of direct linkage of nascent actin filaments to specific membrane sites to which Las17 has been recruited. Overall, we propose that Las17 functions as the key initiator of de novo actin filament formation at endocytic sites by nucleating, elongating and tethering nascent filaments which then serve as a platform for Arp2/3 recruitment and function.
Collapse
Affiliation(s)
- Ellen G. Allwood
- Department of Biomedical Science, Firth Court, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | - Joe J. Tyler
- Department of Biomedical Science, Firth Court, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | - Agnieszka N. Urbanek
- Department of Biomedical Science, Firth Court, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | | | - Kathryn R. Ayscough
- Department of Biomedical Science, Firth Court, University of Sheffield, Sheffield S10 2TN, United Kingdom
- * E-mail:
| |
Collapse
|
11
|
Hoshi HO, Zheng L, Ohta A, Horiuchi H. A Wiskott-Aldrich syndrome protein is involved in endocytosis in Aspergillus nidulans. Biosci Biotechnol Biochem 2016; 80:1802-12. [PMID: 26927610 DOI: 10.1080/09168451.2016.1148580] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Endocytosis is vital for hyphal tip growth in filamentous fungi and is involved in the tip localization of various membrane proteins. To investigate the function of a Wiskott-Aldrich syndrome protein (WASP) in endocytosis of filamentous fungi, we identified a WASP ortholog-encoding gene, wspA, in Aspergillus nidulans and characterized it. The wspA product, WspA, localized to the tips of germ tubes during germination and actin rings in the subapical regions of mature hyphae. wspA is essential for the growth and functioned in the polarity establishment and maintenance during germination of conidia. We also investigated its function in endocytosis and revealed that endocytosis of SynA, a synaptobrevin ortholog that is known to be endocytosed at the subapical regions of hyphal tips in A. nidulans, did not occur when wspA expression was repressed. These results suggest that WspA plays roles in endocytosis at hyphal tips and polarity establishment during germination.
Collapse
Affiliation(s)
- Hiro-Omi Hoshi
- a Department of Biotechnology , The University of Tokyo , Tokyo , Japan
| | - Lu Zheng
- a Department of Biotechnology , The University of Tokyo , Tokyo , Japan
| | - Akinori Ohta
- a Department of Biotechnology , The University of Tokyo , Tokyo , Japan
| | - Hiroyuki Horiuchi
- a Department of Biotechnology , The University of Tokyo , Tokyo , Japan
| |
Collapse
|
12
|
New Regulators of Clathrin-Mediated Endocytosis Identified in Saccharomyces cerevisiae by Systematic Quantitative Fluorescence Microscopy. Genetics 2015; 201:1061-70. [PMID: 26362318 DOI: 10.1534/genetics.115.180729] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 09/07/2015] [Indexed: 11/18/2022] Open
Abstract
Despite the importance of clathrin-mediated endocytosis (CME) for cell biology, it is unclear if all components of the machinery have been discovered and many regulatory aspects remain poorly understood. Here, using Saccharomyces cerevisiae and a fluorescence microscopy screening approach we identify previously unknown regulatory factors of the endocytic machinery. We further studied the top scoring protein identified in the screen, Ubx3, a member of the conserved ubiquitin regulatory X (UBX) protein family. In vivo and in vitro approaches demonstrate that Ubx3 is a new coat component. Ubx3-GFP has typical endocytic coat protein dynamics with a patch lifetime of 45 ± 3 sec. Ubx3 contains a W-box that mediates physical interaction with clathrin and Ubx3-GFP patch lifetime depends on clathrin. Deletion of the UBX3 gene caused defects in the uptake of Lucifer Yellow and the methionine transporter Mup1 demonstrating that Ubx3 is needed for efficient endocytosis. Further, the UBX domain is required both for localization and function of Ubx3 at endocytic sites. Mechanistically, Ubx3 regulates dynamics and patch lifetime of the early arriving protein Ede1 but not later arriving coat proteins or actin assembly. Conversely, Ede1 regulates the patch lifetime of Ubx3. Ubx3 likely regulates CME via the AAA-ATPase Cdc48, a ubiquitin-editing complex. Our results uncovered new components of the CME machinery that regulate this fundamental process.
Collapse
|