Molecular Mechanisms of Endocytosis: Defining the Role of Hrs-2

The University Of Texas Health Science Center At Houston, Houston TX

Investigators

Abstract

Endocytosis is required for the uptake of essential nutrients from the extracellular environment as well as to retrieve proteins and lipids that are added to the plasma membrane during fusion of regulated and constitutive secretory vesicles. A role for the actin cytoskeleton in endocytosis has been controversial. Hrs-2 is a protein that has been localized on endosomes by light and electron microscopy and interacts with eps15, a protein required for endocytosis, suggesting that hrs-2 may play a role in endocytosis. Although actin and hrs-2 do not directly interact, hrs-2 interacts with an actin binding protein, actinin-4. The interaction of hrs-2 with actinin-4 suggests a mechanism by which endosomes interact with the actin cytoskeleton, and fragments of hrs-2 that block its association with actinin-4 inhibit endosome/actin association. The experiments proposed will characterize the interaction of hrs-2 with actinin-4, and examine the role of hrs-2/ actinin-4 interactions in endocytosis. Biochemical, in situ and in vitro trafficking assays, will be used to test the notion that hrs-2 acts as a link between endosomes and actin via specific protein interactions with actinin-4, and to understand the role of this interaction in endocytic trafficking.