HIP1 and HIP12 display differential binding to F-actin, AP2, and clathrin. Identification of a novel interaction with clathrin light chain.
ABSTRACT Huntingtin-interacting protein 1 (HIP1) and HIP12 are orthologues of Sla2p, a yeast protein with essential functions in endocytosis and regulation of the actin cytoskeleton. We now report that HIP1 and HIP12 are major components of the clathrin coat that interact but differ in their ability to bind clathrin and the clathrin adaptor AP2. HIP1 contains a clathrin-box and AP2 consensus-binding sites that display high affinity binding to the terminal domain of the clathrin heavy chain and the ear domain of the AP2 alpha subunit, respectively. These consensus sites are poorly conserved in HIP12 and correspondingly, HIP12 does not bind to AP2 nor does it demonstrate high affinity clathrin binding. Moreover, HIP12 co-sediments with F-actin in contrast to HIP1, which exhibits no interaction with actin in vitro. Despite these differences, both proteins efficiently stimulate clathrin assembly through their central helical domain. Interestingly, in both HIP1 and HIP12, this domain binds directly to the clathrin light chain. Our data suggest that HIP1 and HIP12 play related yet distinct functional roles in clathrin-mediated endocytosis.
Article: Huntingtin-interacting protein 1-related is required for accurate congression and segregation of chromosomes.[show abstract] [hide abstract]
ABSTRACT: Huntingtin-interacting protein 1-related (HIP1r) is known to function in clathrin-mediated endocytosis and regulation of the actin cytoskeleton, which occurs continuously in non-dividing cells. This study reports a new function for HIP1r in mitosis. Green fluorescent protein-fused HIP1r localizes to the mitotic spindles. Depletion of HIP1r by RNA interference induces misalignment of chromosomes and prolonged mitosis, which is associated with decreased proliferation of HIP1r-deficeint cells. Chromosome misalignment leads to missegregation and ultimately production of multinucleated cells. Depletion of HIP1r causes persistent activation of the spindle checkpoint in misaligned chromosomes. These findings suggest that HIP1r plays an important role in regulating the attachment of spindle microtubules to chromosomes during mitosis, an event that is required for accurate congression and segregation of chromosomes. This finding may provide new insights that improve the understanding of various human diseases involving HIP1r as well as its fusion genes.BMB reports 12/2010; 43(12):795-800. · 1.72 Impact Factor