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 scission 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 effectors of its GTPase activity. The interaction of dynamin with SH3 domain-containing proteins is of particular interest since SH3 domains are known to mediate protein-protein interactions in signal transducing complexes.

A binding site for SH3 domains targets dynamin to coated pits.

Dynamin is a GTPase that plays a critical role in the very early stages of endocytosis, regulating the scission of clathrin-coated and non-clathrin-coated pits from the plasma membrane. While the ligands through which dynamin exerts its in vivo effects are unknown, dynamin exhibits in vitro binding to several proteins containing Src homology 3 (SH3) domains, as well as to microtubules and anionic phospholipids, via a basic, proline-rich C-terminal domain. To begin to identify the in vivo binding partners of dynamin, we have examined by immunofluorescence the association of mutant and wild-type forms of dynamin with plasma membranes prepared by sonication of transiently transfected cells.

Molecular analysis of a cytoplasmic dynein light intermediate chain reveals homology to a family of ATPases.

Cytoplasmic dynein is a multi-subunit complex involved in retrograde organelle transport and some aspects of mitosis. In previous work we have cloned and sequenced cDNAs encoding the rat cytoplasmic dynein heavy and intermediate chains. Here we report the cloning of the remaining class of cytoplasmic dynein subunits, which we refer to as the light intermediate chains (LICs: 53-59 kDa).

Microtubules and Src homology 3 domains stimulate the dynamin GTPase via its C-terminal domain.

Dynamin is a 100-kDa GTPase that plays a critical role in the initial stages of endocytosis. Dynamin binds to microtubules, which potently stimulate its GTPase activity. Binding to Src homology 3 (SH3) domains of proteins involved in signal transduction has also recently been reported.

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 Drosophila gene shibire, mutations in which block the recycling of synaptic vesicles and, more generally, the formation of coated and non-coated vesicles at the plasma membrane. We have now transfected cultured mammalian COS-7 cells with both wild-type and mutant dynamin cDNAs.