Control of Organelle Movements and Endoplasmic Reticulum Extension Powered by Kinesin and Cytoplasmic Dynein

This chapter focuses on the current understanding of the molecular basis of organelle motility and speculates on how organelle motility may be controlled. It discusses several sites for the regulation of organelle motility; this regulation is likely to involve not only the motors and their accessory factors but also the organelle binding sites that are thought to determine directionality. Other microtubule-associated proteins may affect motility by forming a stable linkage between an organelle and a microtubule or by simply coating the microtubules to block the binding sites for motors. As per study, the transport of vesicular organelles and endoplasmic reticulum (ER) components along microtubules requires the microtubule-based motors––kinesin and cytoplasmic dynein. These motors are clearly the enzymes that power organelle movements, they require additional cytoplasmic components for the reconstitution of a motile organelle translocation complex, and these two microtubule motors can logically carry material outward toward the plus ends of the microtubules (kinesin) or inward toward the minus ends (cytoplasmic dynein). Although a variety of cellular functions, including endocytosis and protein and lipid synthesis and processing, continue in the absence of microtubules, the rates of these processes are often decreased (e.g, the movement of glycolipids to the apical surface of multicystic dysplastic kidney (MCDK) cells).