EFFECTS OF MUTANT RAT DYNAMIN ON ENDOCYTOSIS

Dynamin is a 100-kD microtubule-activated GTPase. Recent evidence has revealed a high degree of sequence homology with the product of the Dr osophila gene shibire, mutations in which block the recycling of synap tic vesicles and, more generally, the formation of coated and non-coat ed vesicles at the plasma membrane. We have now transfected cultured m ammalian COS-7 cells with both wild-type and mutant dynamin cDNAs. Poi nt mutations in the GTP-binding consensus sequence elements of dynamin equivalent to dominant negative mutations in ras, and an NH2-terminal deletion of the entire GTP-binding domain of dynamin, block transferr in uptake and alter the distribution of clathrin heavy chain and alpha -, but not gamma-, adaptin. COOH-terminal deletions reverse these effe cts, identifying this portion of dynamin as a site of interaction with other components of the endocytic pathway. Over-expression of neither wild-type nor mutant forms of dynamin affected the distribution of mi crotubules. These results demonstrate a specific role for dynamin and for GTP in the initial stages of receptor-mediated endocytosis.