The association of dynamin with synaptophysin regulates quantal size and duration of exocytotic events in chromaffin cells.
Although synaptophysin is one of the most abundant integral proteins of synaptic vesicle membranes, its contribution to neurotransmitter release remains unclear. One possibility is that through its association with dynamin it controls the fine tuning of transmitter release. To test this hypothesis, we took advantage of amperometric measurements of quantal catecholamine release from chromaffin cells. First, we showed that synaptophysin and dynamin interact in chromaffin granule-rich fractions and that this interaction relies on the C terminal of synaptophysin. Experimental maneuvers that are predicted to disrupt the association between these two proteins, such as injection of antibodies against dynamin or synaptophysin, or peptides homologous to the C terminal of synaptophysin, increased the quantal size and duration of amperometric spikes. In contrast, the amperometric current that precedes the spike remained unchanged, indicating that synaptophysin/dynamin association does not regulate the initial fusion pore, but it appears to target a later step of exocytosis to control the amount of catecholamines released during a single vesicle fusion event.
González-Jamett
Arlek M
AM
Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Playa Ancha, Valparaíso 2340000, Chile.
Báez-Matus
Ximena
X
Hevia
Montserrat A
MA
Guerra
María José
MJ
Olivares
María José
MJ
Martínez
Agustín D
AD
Neely
Alan
A
Cárdenas
Ana M
AM
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000378:metabolism* / Q000648:ultrastructure; D002837:Chromaffin Granules / Q000187:drug effects / Q000378:metabolism; D034281:Dynamins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D004563:Electrochemistry / Q000379:methods; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D047468:Immunoprecipitation / Q000379:methods; D008845:Microinjections; D011485:Protein Binding / Q000502:physiology; D054730:Protein Interaction Domains and Motifs / Q000502:physiology; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D016708:Synaptophysin / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D050988:Vesicle-Associated Membrane Protein 2 / Q000378:metabolism
D000906:Antibodies; D016708:Synaptophysin; D050988:Vesicle-Associated Membrane Protein 2; D034281:Dynamins