title: Strain-induced proliferation requires the phosphatidylinositol 3-kinase/AKT/glycogen synthase kinase pathway.
abstract: The intestinal epithelium is repetitively deformed by shear, peristalsis, and villous motility. Such repetitive deformation stimulates the proliferation of intestinal epithelial cells on collagen or laminin substrates via ERK, but the upstream mediators of this effect are poorly understood. We hypothesized that the phosphatidylinositol 3-kinase (PI3K)/AKT cascade mediates this mitogenic effect. PI3K, AKT, and glycogen synthase kinase-3beta (GSK-3beta) were phosphorylated by 10 cycles/min strain at an average 10% deformation, and pharmacologic blockade of these molecules or reduction by small interfering RNA (siRNA) prevented the mitogenic effect of strain in Caco-2 or IEC-6 intestinal epithelial cells. Strain MAPK activation required PI3K but not AKT. AKT isoform-specific siRNA transfection demonstrated that AKT2 but not AKT1 is required for GSK-3beta phosphorylation and the strain mitogenic effect. Furthermore, overexpression of AKT1 or an AKT chimera including the PH domain and hinge region of AKT2 and the catalytic domain and C-tail of AKT1 prevented strain activation of GSK-3beta, but overexpression of AKT2 or a chimera including the PH domain and hinge region of AKT1 and the catalytic domain and C-tail of AKT2 did not. These data delineate a role for PI3K, AKT2, and GSK-3beta in the mitogenic effect of strain. PI3K is required for both ERK and AKT2 activation, whereas AKT2 is sequentially required for GSK-3beta. Furthermore, AKT2 specificity requires its catalytic domain and tail region. Manipulating this pathway may prevent mucosal atrophy and maintain the mucosal barrier in conditions such as ileus, sepsis, and prolonged fasting when peristalsis and villous motility are decreased and the mucosal barrier fails.
authors.affiliation: Department of Surgery, John D. Dingell Veterans Affairs Medical Center, Detroit, Michigan 48301, USA.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Gayer
authors.forename: Lakshmi S
authors.initials: LS
authors.lastname: Chaturvedi
authors.forename: Shouye
authors.initials: S
authors.lastname: Wang
authors.forename: David H
authors.initials: DH
authors.lastname: Craig
authors.forename: Thomas
authors.initials: T
authors.lastname: Flanigan
authors.forename: Marc D
authors.initials: MD
authors.lastname: Basson
mesh_terms: D002460:Cell Line; D049109:Cell Proliferation; D003094:Collagen / Q000378:metabolism; D038341:Glycogen Synthase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009218:Myosins / Q000037:antagonists & inhibitors / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013314:Stress, Mechanical; D013312:Stress, Physiological / Q000502:physiology*; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D003094:Collagen; D038341:Glycogen Synthase Kinases; D007527:Isoenzymes; D020928:Mitogen-Activated Protein Kinases; D009218:Myosins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D011994:Recombinant Proteins; D019061:src-Family Kinases