Overexpression of wild-type and mutant mucolipin proteins in mammalian cells: effects on the late endocytic compartment organization

Mucolipin-1 is a 65-kDa membrane protein encoded by the MCOLN1 gene, which is mutated in patients with mucolipidosis type IV (MLIV), a rare neurodegenerative lysosomal storage disorder. We studied the subcellular localization of wild-type and three different mutant forms (T232P, F408del and F465L) of mucolipin by expressing Myc-tagged proteins in HeLa cells. The overexpressed wild-type mucolipin colocalizes to late endocytic structures and induces an aberrant distribution of these compartments. F408del and F465L MLIV mutant proteins show a distribution similar to the wild-type protein, whereas T232P is retained in the endoplasmic reticulum. Among the mutants, only F408del induces a redistribution of the late endocyctic compartment. These findings suggest that the overexpression of the mucolipin cation channel influences the dynamic equilibrium of late endocytic compartments. (C) 2004 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.