Endocytic Internalization in Budding Yeast Requires Coordinated Actin Nucleation and Myosin Motor Activity

Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA.
Developmental Cell (Impact Factor: 9.71). 08/2006; 11(1):33-46. DOI: 10.1016/j.devcel.2006.05.008
Source: PubMed


Actin polymerization essential for endocytic internalization in budding yeast is controlled by four nucleation promoting factors (NPFs) that each exhibits a unique dynamic behavior at endocytic sites. How each NPF functions and is regulated to restrict actin assembly to late stages of endocytic internalization is not known. Quantitative analysis of NPF biochemical activities, and genetic analysis of recruitment and regulatory mechanisms, defined a linear pathway in which protein composition changes at endocytic sites control actin assembly and function. We show that yeast WASP initiates actin assembly at endocytic sites and that this assembly and the recruitment of a yeast WIP-like protein by WASP recruit a type I myosin with both NPF and motor activities. Importantly, type I myosin motor and NPF activities are separable, and both contribute to endocytic coat inward movement, which likely represents membrane invagination. These results reveal a mechanism in which actin nucleation and myosin motor activity cooperate to promote endocytic internalization.

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    • "Early in endocytosis, Syp1 recruits WASP­ but maintains it in an inactive state (Rodal et al., 2003; Sun et al., 2006; Boettner et al., 2009; Feliciano and Di P­ietro, 2012). Upon vesicle maturation, Bzz1 activates WASP­ activity (Sun et al., 2006), thereby inducing a burst of actin polymerization mediated by the ARP­2/3 complex that promotes internalization of endocytic vesicles. Further physiological support for this model has come from studies in neurons (Dharmalingam et al., 2009) and animal cells (Tsujita et al., 2006). "
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    • "Our results suggest that Rbd2 functions in the same molecular pathway as Bzz1 to regulate actin assembly during CME. Bzz1 has been implicated in actin regulation during CME (Sun et al., 2006; Arasada and Pollard, 2011), and its mammalian homologue, syndapin , may also link CME and actin dynamics (Qualmann and Kelly, 2000). Why the bzz1Δ mutation suppresses the early actin-polymerization-phenotype of rbd2Δ cells is not clear. "
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    • "The BAR and F-BAR proteins can bend membranes, sense membrane curvature, and serve as the link between membrane deformation and actin assembly (Aspenstrom, 2009). The F-BAR protein Bzz1 is recruited to cortical patches just prior to initiation of actin polymerization in budding yeast (Sun et al., 2006). The SH3 domain of Bzz1 interacts directly with Las17 and can stimulate actin polymerization that depends on Arp2/3, Las17, Vrp1, and myosin 1 (Soulard et al., 2002, 2005). "
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