Actin-dependent pigment granule transport in retinal pigment epithelial cells.

Since diffusion of particles as large as vesicles or organelles is constrained by the high viscosity of cytoplasm, directed translocation of these particles from one cytoplasmic site to another must be achieved by cytoskeletal intervention. In most cases, this is achieved by attaching the particle to a molecular motor which then navigates along a microtubule or an actin filament track (Fath and Burgess, 1994). Although microtubule-dependent transport in animal cells has been more extensively studied, important roles for actin-dependent transport have also recently been recognized (Langford, 1995).