title: Absence of Shb impairs insulin secretion by elevated FAK activity in pancreatic islets.
abstract: The Src homology-2 domain containing protein B (SHB) has previously been shown to function as a pleiotropic adapter protein, conveying signals from receptor tyrosine kinases to intracellular signaling intermediates. The overexpression of Shb in β-cells promotes β-cell proliferation by increased insulin receptor substrate (IRS) and focal adhesion kinase (FAK) activity, whereas Shb deficiency causes moderate glucose intolerance and impaired first-peak insulin secretion. Using an array of techniques, including live-cell imaging, patch-clamping, immunoblotting, and semi-quantitative PCR, we presently investigated the causes of the abnormal insulin secretory characteristics in Shb-knockout mice. Shb-knockout islets displayed an abnormal signaling signature with increased activities of FAK, IRS, and AKT. β-catenin protein expression was elevated and it showed increased nuclear localization. However, there were no major alterations in the gene expression of various proteins involved in the β-cell secretory machinery. Nor was Shb deficiency associated with changes in glucose-induced ATP generation or cytoplasmic Ca(2+) handling. In contrast, the glucose-induced rise in cAMP, known to be important for the insulin secretory response, was delayed in the Shb-knockout compared with WT control. Inhibition of FAK increased the submembrane cAMP concentration, implicating FAK activity in the regulation of insulin exocytosis. In conclusion, Shb deficiency causes a chronic increase in β-cell FAK activity that perturbs the normal insulin secretory characteristics of β-cells, suggesting multi-faceted effects of FAK on insulin secretion depending on the mechanism of FAK activation.
authors.affiliation: Department of Medical Cell BiologyUppsala University, Box 571, Husargatan 3, 75123 Uppsala, SwedenDepartment of NeuroscienceUppsala University, Uppsala, Sweden.
authors.forename: Ida
authors.initials: I
authors.lastname: Alenkvist
authors.affiliation: Department of Medical Cell BiologyUppsala University, Box 571, Husargatan 3, 75123 Uppsala, SwedenDepartment of NeuroscienceUppsala University, Uppsala, Sweden.
authors.forename: Oleg
authors.initials: O
authors.lastname: Dyachok
authors.affiliation: Department of Medical Cell BiologyUppsala University, Box 571, Husargatan 3, 75123 Uppsala, SwedenDepartment of NeuroscienceUppsala University, Uppsala, Sweden.
authors.forename: Geng
authors.initials: G
authors.lastname: Tian
authors.affiliation: Department of Medical Cell BiologyUppsala University, Box 571, Husargatan 3, 75123 Uppsala, SwedenDepartment of NeuroscienceUppsala University, Uppsala, Sweden.
authors.forename: Jia
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Medical Cell BiologyUppsala University, Box 571, Husargatan 3, 75123 Uppsala, SwedenDepartment of NeuroscienceUppsala University, Uppsala, Sweden.
authors.forename: Saba
authors.initials: S
authors.lastname: Mehrabanfar
authors.affiliation: Department of Medical Cell BiologyUppsala University, Box 571, Husargatan 3, 75123 Uppsala, SwedenDepartment of NeuroscienceUppsala University, Uppsala, Sweden.
authors.forename: Yang
authors.initials: Y
authors.lastname: Jin
authors.affiliation: Department of Medical Cell BiologyUppsala University, Box 571, Husargatan 3, 75123 Uppsala, SwedenDepartment of NeuroscienceUppsala University, Uppsala, Sweden.
authors.forename: Bryndis
authors.initials: B
authors.lastname: Birnir
authors.affiliation: Department of Medical Cell BiologyUppsala University, Box 571, Husargatan 3, 75123 Uppsala, SwedenDepartment of NeuroscienceUppsala University, Uppsala, Sweden anders.tengholm@mcb.uu.se michael.welsh@mcb.uu.se.
authors.forename: Anders
authors.initials: A
authors.lastname: Tengholm
authors.affiliation: Department of Medical Cell BiologyUppsala University, Box 571, Husargatan 3, 75123 Uppsala, SwedenDepartment of NeuroscienceUppsala University, Uppsala, Sweden anders.tengholm@mcb.uu.se michael.welsh@mcb.uu.se.
authors.forename: Michael
authors.initials: M
authors.lastname: Welsh
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D005089:Exocytosis / Q000235:genetics; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism*; D015870:Gene Expression; D005947:Glucose / Q000494:pharmacology; D015151:Immunoblotting; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence / Q000379:methods; D011518:Proto-Oncogene Proteins / Q000172:deficiency* / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051176:beta Catenin / Q000378:metabolism; D020826:rab3A GTP-Binding Protein / Q000235:genetics
chemical_list: D015220:Calcium Channels; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D011518:Proto-Oncogene Proteins; C085634:Shb protein, mouse; D051176:beta Catenin; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D051416:Focal Adhesion Protein-Tyrosine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020826:rab3A GTP-Binding Protein; D005947:Glucose; D002118:Calcium
keywords: FAK; Src homology 2; cAMP; insulin secretion