ROLE OF THE BASIC, PROLINE-RICH REGION OF DYNAMIN IN SRC HOMOLOGY-3 DOMAIN BINDING AND ENDOCYTOSIS

The GTPase dynamin has been implicated in the regulation of the scissi on of coated and noncoated pits during the early stages of endocytosis . Various macromolecules including microtubules, acidic phospholipids, and Src homology 3 (SH3) domains have been shown to interact with the basic, proline-rich region of dynamin and act as effecters of its GTP ase activity, The interaction of dynamin with SH3 domain-containing pr oteins is of particular interest since SH3 domains are known to mediat e protein-protein interactions in signal transducing complexes, In thi s study, we have systematically defined three distinct SH3 binding reg ions within the dynamin proline-rich C terminus, These binding regions conform to either the Class I or II SH3 binding consensus sequence, a nd their location coincides with a region previously shown to be impor tant in the colocalization of dynamin with clathrin-coated pits, Two o f these SH3 binding regions are well conserved among four dynamin isof orms, and we show that the overall binding pattern for SH3 domains is comparable among the isoforms, We also demonstrate that neither transf errin nor platelet-derived growth factor receptor uptake is restored u pon removal of the basic, proline-rich region in a dominant negative d ynamin GTP binding mutant. Together with earlier evidence from our lab oratory, these findings suggest that SH3 domains may serve to target d ynamin to coated pits and are not the direct targets of dominant inhib itory mutants of dynamin.