Endocytosis and Cytoskeleton

This chapter describes the various emerging evidence supporting the involvement of actin dynamics in endocytosis. It also briefly discusses the possible roles for microtubules during the initial and later phases of the endocytic process and describes the known molecular circuitries that link and integrate endocytosis and actin dynamics. Endocytosis of membrane receptors is governed by a complex structural machinery, which is in turn controlled by various accessory regulatory proteins. Links between endocytosis and the actin cytoskeleton have been revealed by a number of studies in yeast A variety of the so-called "end" or "dim" mutations, isolated in screening for endocytic defects. Various activators of Arp2/3, including Las17/Beelp, Abpl, and the type I myosin Myo3/5p have been reported to affect endocytosis to various extents. The role of microtubules in the endocytic process has been established mainly with the use of microtubule depolymerizing drugs, such as nocodazole. In cells kept in suspension, but not in cells grown on substrates, nocodazole was reported to reduce by 40% the initial rate of transferrin receptor internalization. This suggests that the overall structural organization of a cell might affect microtubule organization and dynamics, leading to alterations in membrane plasticity, and consequently affecting the ability of a receptor to be recruited to the invaginating clathrin-coated pit.