Regulated exocytosis and kiss-and-run of synaptic-like microvesicles in INS-1 and primary rat beta-cells.
We have applied cell-attached capacitance measurements to investigate whether synaptic-like microvesicles (SLMVs) undergo regulated exocytosis in insulinoma and primary pancreatic beta-cells. SLMV and large dense-core vesicle (LDCV) exocytosis was increased 1.6- and 2.4-fold upon stimulation with 10 mmol/l glucose in INS-1 cells. Exocytosis of both types of vesicles was coupled to Ca(2+) entry through l-type channels. Thirty percent of SLMV exocytosis in INS-1 and rat beta-cells was associated with transient capacitance increases consistent with kiss-and-run. Elevation of intracellular cAMP (5 micromol/l forskolin) increased SLMV exocytosis 1.6-fold and lengthened the duration of kiss-and-run events in rat beta-cells. Experiments using isolated inside-out patches of INS-1 cells revealed that the readily releasable pool (RRP) of SLMVs preferentially undergoes kiss-and-run exocytosis (67%), is proportionally larger than the LDCV RRP, and is depleted more quickly upon Ca(2+) stimulation. We conclude that SLMVs undergo glucose-regulated exocytosis and are capable of high turnover. Following kiss-and-run exocytosis, the SLMV RRP may be reloaded with gamma-aminobutyric acid and undergo several cycles of exo- and endocytosis. Our observations support a role for beta-cell SLMVs in a synaptic-like function of rapid intra-islet signaling.
MacDonald
Patrick E
PE
Section of Diabetes, Metabolism and Endocrinology, Lund University, Lund, Sweden. patrick.macdonald@mphy.lu.se
Obermüller
Stefanie
S
Vikman
Jenny
J
Galvanovskis
Juris
J
Rorsman
Patrik
P
Eliasson
Lena
L
D000818:Animals; D002118:Calcium / Q000502:physiology; D015220:Calcium Channels / Q000502:physiology; D045744:Cell Line, Tumor; D002462:Cell Membrane; D002474:Cell-Free System; D005576:Colforsin / Q000494:pharmacology; D005089:Exocytosis / Q000502:physiology*; D005947:Glucose / Q000494:pharmacology; D007340:Insulinoma / Q000378:metabolism*; D007515:Islets of Langerhans / Q000502:physiology* / Q000648:ultrastructure; D051381:Rats; D022142:Secretory Vesicles / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D015220:Calcium Channels; D005576:Colforsin; D005680:gamma-Aminobutyric Acid; D005947:Glucose; D002118:Calcium