Rab-interacting lysosomal protein (RILP): the Rab7 effector required for transport to lysosomes

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Abstract
Rab7 is a small GTPase that controls transport to endocytic degradative compartments. Here we report the identification of a novel 45 kDa protein that specifically binds Rab7GTP at its C‐terminus. This protein contains a domain comprising two coiled‐coil regions typical of myosin‐like proteins and is found mainly in the cytosol. We named it RILP (Rab‐interacting lysosomal protein) since it can be recruited efficiently on late endosomal and lysosomal membranes by Rab7GTP. RILP‐C33 (a truncated form of the protein lacking the N‐terminal half) strongly inhibits epidermal growth factor and low‐density lipoprotein degradation, and causes dispersion of lysosomes similarly to Rab7 dominant‐negative mutants. More importantly, expression of RILP reverses/prevents the effects of Rab7 dominant‐negative mutants. All these data are consistent with a model in which RILP represents a downstream effector for Rab7 and both proteins act together in the regulation of late endocytic traffic.