Endocytic recycling is critical for many cellular events, including the recycling of important nutrient receptors, such as the transferrin receptor and the low-density lipoprotein receptor, for reiterative rounds of ligand uptake, and also the redistribution of integrins from the retracting edges to the leading edge of cells to mediate their motility. Despite these many documented important roles, how proteins are sorted during endocytic recycling, a process that critically regulates their function remains poorly understood. In preliminary studies, we have identified ACAP1 to function in the sorting of cargo proteins that exemplify constitutive and regulated recycling at the recycling endosome, with its phosphorylation providing an explanation for how it is able to participate in both processes. Moreover, we have found that overexpression of ACAP1 induces the coating of endosomes. Thus, in Aim 1, we will provide a more definitive test for whether ACAP1 functions as a coat protein using a reconstitution system that generates transport carriers from the recycling endosome, followed by approaches which will either prove that ACAP1 alone functions as a coat protein or that it functions in conjunction with other proteins as part of coat complex.
In Aim 2, because the critical nexus in regulated transport involves the signaling process interfacing with the transport process, we will identify kinase(s) predicted to directly phosphorylate ACAP1.
In Aim 3, as we have identified sorting signals recognized by ACAP1 for constitutive recycling, we will also identify sorting signal(s) recognized by ACAP1 for regulated recycling, using integrin beta1 as the model system. This finding will then enable us to further elucidate how ACAP1 is able to participate in both constitutive and regulated recycling. Moreover, the identification of recycling sorting signal(s) in integrin beta1 will allow us to test more definitively whether integrin recycling plays a critical role in cell migration, and thereby demonstrating that a better understanding of endocytic recycling has important implications to understanding other cellular events.
| Li, Jian; Hsu, Victor W (2015) An ACAP1 coat complex acting in endocytic recycling. Methods Cell Biol 130:81-99 |
| Pang, Xiaoyun; Fan, Jun; Zhang, Yan et al. (2014) A PH domain in ACAP1 possesses key features of the BAR domain in promoting membrane curvature. Dev Cell 31:73-86 |
| Li, Jian; Malaby, Andrew W; Famulok, Michael et al. (2012) Grp1 plays a key role in linking insulin signaling to glut4 recycling. Dev Cell 22:1286-98 |
| Hsu, Victor W; Bai, Ming; Li, Jian (2012) Getting active: protein sorting in endocytic recycling. Nat Rev Mol Cell Biol 13:323-8 |
| Bai, Ming; Pang, Xiaoyun; Lou, Jizhong et al. (2012) Mechanistic insights into regulated cargo binding by ACAP1 protein. J Biol Chem 287:28675-85 |
| Bai, Ming; Gad, Helge; Turacchio, Gabriele et al. (2011) ARFGAP1 promotes AP-2-dependent endocytosis. Nat Cell Biol 13:559-67 |
| Gu, Zhizhan; Noss, Erika H; Hsu, Victor W et al. (2011) Integrins traffic rapidly via circular dorsal ruffles and macropinocytosis during stimulated cell migration. J Cell Biol 193:61-70 |
| Hsu, Victor W; Prekeris, Rytis (2010) Transport at the recycling endosome. Curr Opin Cell Biol 22:528-34 |
| Li, Jian; Peters, Peter J; Bai, Ming et al. (2007) An ACAP1-containing clathrin coat complex for endocytic recycling. J Cell Biol 178:453-64 |
