SUR1 regulates PKA-independent cAMP-induced granule priming in mouse pancreatic B-cells.
Measurements of membrane capacitance were applied to dissect the cellular mechanisms underlying PKA-dependent and -independent stimulation of insulin secretion by cyclic AMP. Whereas the PKA-independent (Rp-cAMPS-insensitive) component correlated with a rapid increase in membrane capacitance of approximately 80 fF that plateaued within approximately 200 ms, the PKA-dependent component became prominent during depolarizations >450 ms. The PKA-dependent and -independent components of cAMP-stimulated exocytosis differed with regard to cAMP concentration dependence; the K(d) values were 6 and 29 micro M for the PKA-dependent and -independent mechanisms, respectively. The ability of cAMP to elicit exocytosis independently of PKA activation was mimicked by the selective cAMP-GEFII agonist 8CPT-2Me-cAMP. Moreover, treatment of B-cells with antisense oligodeoxynucleotides against cAMP-GEFII resulted in partial (50%) suppression of PKA-independent exocytosis. Surprisingly, B-cells in islets isolated from SUR1-deficient mice (SUR1(-/-) mice) lacked the PKA-independent component of exocytosis. Measurements of insulin release in response to GLP-1 stimulation in isolated islets from SUR1(-/-) mice confirmed the complete loss of the PKA-independent component. This was not attributable to a reduced capacity of GLP-1 to elevate intracellular cAMP but instead associated with the inability of cAMP to stimulate influx of Cl(-) into the granules, a step important for granule priming. We conclude that the role of SUR1 in the B cell extends beyond being a subunit of the plasma membrane K(ATP)-channel and that it also plays an unexpected but important role in the cAMP-dependent regulation of Ca(2+)-induced exocytosis.
Eliasson
Lena
L
Department of Molecular and Cellular Physiology, Institute of Physiological Sciences, SE-221 84 Lund, Sweden.
Ma
Xiaosong
X
Renström
Erik
E
Barg
Sebastian
S
Berggren
Per-Olof
PO
Galvanovskis
Juris
J
Gromada
Jesper
J
Jing
Xingjun
X
Lundquist
Ingmar
I
Salehi
Albert
A
Sewing
Sabine
S
Rorsman
Patrik
P
D018528:ATP-Binding Cassette Transporters; D000818:Animals; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D025802:Electric Capacitance; D004594:Electrophysiology; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology; D005934:Glucagon / Q000494:pharmacology; D052216:Glucagon-Like Peptide 1; D005947:Glucose / Q000494:pharmacology; D020662:Guanine Nucleotide Exchange Factors / Q000819:agonists / Q000502:physiology; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D010446:Peptide Fragments / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D011498:Protein Precursors / Q000494:pharmacology; D011955:Receptors, Drug / Q000502:physiology*; D022142:Secretory Vesicles / Q000502:physiology*; D064233:Sulfonylurea Receptors; D013997:Time Factors
D018528:ATP-Binding Cassette Transporters; C577508:Abcc8 protein, mouse; D020662:Guanine Nucleotide Exchange Factors; D007328:Insulin; D010446:Peptide Fragments; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011498:Protein Precursors; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D005947:Glucose