TY - JOUR
T1 - An internal GAP domain negatively regulates presynaptic dynamin in vivo
T2 - A two-step model for dynamin function
AU - Narayanan, Radhakrishnan
AU - Leonard, Marilyn
AU - Byeong, Doo Song
AU - Schmid, Sandra L.
AU - Ramaswami, Mani
PY - 2005/4/11
Y1 - 2005/4/11
N2 - The mechanism by which the self-assembling GTPase dynamin functions in vesicle formation remains controversial. Point mutations in shibire, the Drosophila dynamin, cause temperature-sensitive (ts) defects in endocytosis. We show that the ts2 mutation, which occurs in the switch 2 region of dynamin's GTPase domain, compromises GTP binding affinity. Three second-site suppressor mutations, one in the switch 1 region of the GTPase domain and two in the GTPase effector domain (GED), dynamin's putative GAP, fully rescue the shi ts2 defects in synaptic vesicle recycling. The functional rescue in vivo correlates with a reduction in both the basal and assembly-stimulated GTPase activity in vitro. These findings demonstrate that GED is indeed an internal dynamin GAP and establish that, as for other GTPase superfamily members, dynamin's function in vivo is negatively regulated by its GAP activity. Based on these and other observations, we propose a two-step model for dynamin during vesicle formation in which an early regulatory GTPase-like function precedes late, assembly-dependent steps during which GTP hydrolysis is required for vesicle release.
AB - The mechanism by which the self-assembling GTPase dynamin functions in vesicle formation remains controversial. Point mutations in shibire, the Drosophila dynamin, cause temperature-sensitive (ts) defects in endocytosis. We show that the ts2 mutation, which occurs in the switch 2 region of dynamin's GTPase domain, compromises GTP binding affinity. Three second-site suppressor mutations, one in the switch 1 region of the GTPase domain and two in the GTPase effector domain (GED), dynamin's putative GAP, fully rescue the shi ts2 defects in synaptic vesicle recycling. The functional rescue in vivo correlates with a reduction in both the basal and assembly-stimulated GTPase activity in vitro. These findings demonstrate that GED is indeed an internal dynamin GAP and establish that, as for other GTPase superfamily members, dynamin's function in vivo is negatively regulated by its GAP activity. Based on these and other observations, we propose a two-step model for dynamin during vesicle formation in which an early regulatory GTPase-like function precedes late, assembly-dependent steps during which GTP hydrolysis is required for vesicle release.
UR - http://www.scopus.com/inward/record.url?scp=17644424000&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=17644424000&partnerID=8YFLogxK
U2 - 10.1083/jcb.200502042
DO - 10.1083/jcb.200502042
M3 - Article
C2 - 15824135
AN - SCOPUS:17644424000
SN - 0021-9525
VL - 169
SP - 117
EP - 126
JO - Journal of Cell Biology
JF - Journal of Cell Biology
IS - 1
ER -