Dymple, a novel dynamin-like high molecular weight GTPase lacking a proline-rich carboxyl-terminal domain in mammalian cells

Abstract

We have cloned human dymple, a novel dynamin family member. The full- length cDNA sequence encodes a protein composed of 736 amino acids with a molecular mass of 80 kDa. This amino acid sequence most resembles yeast DNM1P and VPS1P. Dymple lacks a proline-rich carboxyl-terminal domain through which dynamin binds to SH3 domains to be activated. Northern blot analysis revealed two transcript sizes of 2.5 and 4.2 kilobases with alternative polyadenylation at the highest levels in brain, skeletal muscle, and testis. It was further established that there are three patterns of alternative splicing producing in-frame deletions in the coding sequence of dymple in a tissue-specific manner. When overexpressed, wild-type dymple exhibited a punctate perinuclear cytoplasmic pattern, whereas an amino-terminal deletion mutant formed large aggregates bounded by a trans-Golgi network marker. Since dynamin participates in clathrin-mediated endocytosis through a well- characterized mechanism, the existence of a dynamin-like molecule in each specific vesicle transport pathway has been predicted. Our findings suggest that dymple may be the first example of such a subfamily in mammalian cells other than dynamin itself, although its precise role and membrane localization remain to be resolved.