A Hip1R–cortactin complex negatively regulates actin assembly associated with endocytosis

Abstract

Actin polymerization plays a critical role in clathrinmediated endocytosis in many cell types, but how polymerization is regulated is not known. Hip1R may negatively regulate actin assembly during endocytosis because its depletion increases actin assembly at endocytic sites. Here, we show that the C-terminal proline-rich domain of Hip1R binds to the SH3 domain of cortactin, a protein that binds to dynamin, actin filaments and the Arp2/3 complex. We demonstrate that Hip1R deleted for the cortactin-binding site loses its ability to rescue fully the formation of abnormal actin structures at endocytic sites induced by Hip1R siRNA. To determine when this complex might function during endocytosis, we performed live cell imaging. The maximum in vivo recruitment of Hip1R, clathrin and cortactin to endocytic sites was coincident, and all three proteins disappeared together upon formation of a clathrin-coated vesicle. Finally, we showed that Hip1R inhibits actin assembly by forming a complex with cortactin that blocks actin filament barbed end elongation.

Protein Kinase Cδ and Calmodulin Regulate Epidermal Growth Factor Receptor Recycling from Early Endosomes through Arp2/3 Complex and Cortactin

“…Hip1R negatively regulates cortactin-stimulated actin polymerization to guarantee a transient and productive interaction between coated pits and actin during vesicle internalization (Engqvist-Goldstein et al, 2004;Le Clainche et al, 2007). In fact, this same proposal could be formulated in our study on CaM/cortactin and vesicles formation in endosomes.…”

“…In trafficking events, cortactin has been involved in clathrin-mediated endocyto-sis as well as in pinocytosis, regulation of epidermal growth factor receptor (EGFR) degradation, or endosomal positioning (McNiven et al, 2000;Cao et al, 2003Cao et al, , 2005Lynch et al, 2003;Cabezas et al, 2005;Merrifield et al, 2005;Sauvonnet et al, 2005;Timpson et al, 2005;Zhu et al, 2005;Mettlen et al, 2006;Le Clainche et al, 2007).…”

The Mammalian Actin-Binding Protein 1 Is Critical for Spreading and Intraluminal Crawling of Neutrophils under Flow Conditions

“…Less is known about the mammalian ortholog of Sla2p, the Huntingtin-interacting protein-1-related protein (Hip1R). However, it has been shown to bind F-actin, to associate with clathrin-coated vesicles, and to form a complex with cortactin, which acts as a negative regulator of actin polymerization in HeLa cells, suggesting that Hip1R may compensate for the absence of mAbp1 during chemotactic migration (64). Growing evidence supports the concept that mechanical force may be required for the development of adhesion sites by inducing recruitment of additional proteins.…”

Huntingtin-interacting protein 1-related is required for accurate congression and segregation of chromosomes

“…On the other hand, the subcellular distribution of GFP-HIP1r was found to be unique during specific phases of the cell cycle. During interphase, GFP-HIP1r in HeLa cells was found to be associated with clathrin-coated vesicles as previously described (12,13). In metaphase, the fluorescence signal was found to be concentrated to mitotic spindle fibers, as judged by immunostaining of α-tubulin (Fig.…”

“…Several previous reports have shown that these proteins primarily regulate the formation of clathrincoated vesicles and trafficking by associating with actin at the plasma membrane (12,13). However, it was unexpectedly found that embryonic fibroblasts derived from either HIP1 or HIP1r single knockout mice do not have any endocytic defects (3,14,15).…”