CLIP-170, a Cytoplasmic Linker Protein Mediating Interaction of Endosomes with Microtubules

Abstract

Microtubules play a key role in the dynamic spatial organization of the cytoplasmic matrix. They are involved in regulating the structure and positioning of intracellular organelles like the Golgi apparatus and endosomes, and they provide the tracks for directed movement of such organelles [Kreis, 1990]. Membrane-bounded cytoplasmic organelles attach to microtubules, move along or remain stably associated with them, and eventually detach. These interactions of organelles with microtubules appear to be specific. For example, endosomes, but not Golgi elements, reverse their direction of translocation along microtubules upon acidification of the cytoplasm [Heuser, 1989; Parton et al., 1991]. These various interactions require different levels of regulation; specificity and timing of binding and release, positioning, and direction of movement. We postulate, therefore, that different proteins must be involved in the regulation of these interactions of cytoplasmic organelles with microtubules.