Regulation of laminin 1-induced pancreatic beta-cell differentiation by alpha6 integrin and alpha-dystroglycan.
BACKGROUND
The ability to manipulate the development of pancreatic insulin-producing beta cells has implications for the treatment of type 1 diabetes. Previously, we found that laminin-1, a basement membrane trimeric glycoprotein, promotes beta-cell differentiation. We have investigated the mechanism of this effect, using agents that block the receptors for laminin-1, alpha6 integrin, and alpha-dystroglycan (alpha-DG).


METHODS
Dissociated cells from 13.5-day postcoitum (dpc) fetal mouse pancreas were cultured for 4 days with laminin-1, with and without monoclonal antibodies and other agents known to block integrins or alpha-DG. Fetuses fixed in Bouin's solution or fetal pancreas cells fixed in 4% paraformaldehyde were processed for routine histology and for immunohistology to detect hormone expression and bromodeoxyuridine (BrdU) uptake.


RESULTS
Blocking the binding of laminin-1 to alpha6 integrin with a monoclonal antibody, GoH3, abolished cell proliferation (BrdU uptake) and doubled the number of beta cells. Inhibition of molecules involved in alpha6 integrin signaling (phosphotidylinositol 3-kinase, F-actin, or mitogen-activated protein kinase) had a similar effect. Nevertheless, beta cells appeared to develop normally in alpha6 integrin-deficient fetuses. Blocking the binding of laminin-1 to alpha-DG with a monoclonal antibody, IIH6, dramatically decreased the number of beta cells. Heparin, also known to inhibit laminin-1 binding to alpha-DG, had a similar effect. In the presence of heparin, the increase in beta cells in response to blocking alpha integrin with GoH3 was abolished.


CONCLUSIONS
These findings reveal an interplay between alpha6 integrin and alpha-DG to regulate laminin-1-induced beta-cell development. Laminin-I had a dominant effect via alpha-DG to promote cell survival and beta-cell differentiation, which was modestly inhibited by alpha6 signaling.
Jiang
F X
FX
Autoimmunity and Transplantation Division, Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Parkville, Australia.
Georges-Labouesse
E
E
Harrison
L C
LC
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D015703:Antigens, CD / Q000378:metabolism*; D001973:Bromodeoxyuridine / Q000378:metabolism; D002454:Cell Differentiation; D002470:Cell Survival; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D049030:Dystroglycans; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006579:Heterozygote; D006720:Homozygote; D039503:Integrin alpha6; D007515:Islets of Langerhans / Q000378:metabolism*; D007797:Laminin / Q000378:metabolism / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D010179:Pancreas / Q000196:embryology / Q000473:pathology; D051381:Rats; D015398:Signal Transduction; D013997:Time Factors
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D003598:Cytoskeletal Proteins; D004791:Enzyme Inhibitors; D039503:Integrin alpha6; D007797:Laminin; D008562:Membrane Glycoproteins; C121346:laminin 1; D049030:Dystroglycans; D001973:Bromodeoxyuridine