Dynamin-2 regulates fusion pore expansion and quantal release through a mechanism that involves actin dynamics in neuroendocrine chromaffin cells.
Over the past years, dynamin has been implicated in tuning the amount and nature of transmitter released during exocytosis. However, the mechanism involved remains poorly understood. Here, using bovine adrenal chromaffin cells, we investigated whether this mechanism rely on dynamin's ability to remodel actin cytoskeleton. According to this idea, inhibition of dynamin GTPase activity suppressed the calcium-dependent de novo cortical actin and altered the cortical actin network. Similarly, expression of a small interfering RNA directed against dynamin-2, an isoform highly expressed in chromaffin cells, changed the cortical actin network pattern. Disruption of dynamin-2 function, as well as the pharmacological inhibition of actin polymerization with cytochalasine-D, slowed down fusion pore expansion and increased the quantal size of individual exocytotic events. The effects of cytochalasine-D and dynamin-2 disruption were not additive indicating that dynamin-2 and F-actin regulate the late steps of exocytosis by a common mechanism. Together our data support a model in which dynamin-2 directs actin polymerization at the exocytosis site where both, in concert, adjust the hormone quantal release to efficiently respond to physiological demands.
Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Gran Bretaña, Playa Ancha, Valparaíso, Chile.
Arlek M
AM
González-Jamett
Fanny
F
Momboisse
María José
MJ
Guerra
Stéphane
S
Ory
Ximena
X
Báez-Matus
Natalia
N
Barraza
Valerie
V
Calco
Sébastien
S
Houy
Eduardo
E
Couve
Alan
A
Neely
Agustín D
AD
Martínez
Stéphane
S
Gasman
Ana M
AM
Cárdenas
D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000818:Animals; D002395:Catecholamines / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000378:metabolism*; D034285:Dynamin II / Q000502:physiology*; D005089:Exocytosis; D015870:Gene Expression; D008561:Membrane Fusion; D055503:Protein Multimerization; D022142:Secretory Vesicles / Q000378:metabolism
D000199:Actins; D002395:Catecholamines; D034285:Dynamin II