Differentiation state-selective roles of p38 isoforms in human intestinal epithelial cell anoikis.
OBJECTIVE
Little is known of the signaling events implicated in the induction of human enterocytic anoikis. In the present study, we analyzed the role of the stress-activated protein kinase p38 in this process.


METHODS
Anoikis was induced in undifferentiated and differentiated enterocytes by inhibition of focal adhesion kinase (Fak; pharmacologic inhibition or overexpression of a dominant negative form) or beta1 integrins (antibody blocking), or by maintaining cells in suspension. Expression/activation parameters of p38 (isoforms alpha, beta, gamma, delta) and of the Fak/phosphatidylinositol-3-kinase (PI3-K)/Akt anoikis-suppressing pathways were analyzed. Kinase activities of p38 isoforms also were blocked by pharmacologic inhibitors or by overexpression of dominant-negative forms.


RESULTS
(1) p38 activation is sustained transiently after induction of anoikis in both undifferentiated and differentiated enterocytes; (2) such sustenance of p38 activation is associated with a down-regulation of the Fak/PI3-K/Akt pathway; (3) distinct profiles of p38 isoform expression are exhibited by undifferentiated (alpha, beta, gamma) and differentiated (alpha, gamma, delta) enterocytes; (4) none of the 4 known p38 isoforms was found to promote cell survival in either differentiation state; and (5) only p38beta and p38delta are required specifically for anoikis in undifferentiated and differentiated cells, respectively.


CONCLUSIONS
Distinct p38 isoforms play a major role in the induction of enterocytic anoikis and the regulation of such selective p38 isoform-mediated anoikis is linked with the state of cell differentiation. These data provide novel insights into the synchronized regulation of cell survival/death required in the epithelial renewal process along the human intestinal crypt-villus axis.
Vachon
Pierre H
PH
Canadian Institutes of Health Research Group on the Functional Development and Physiopathology of the Digestive Tract, Québec, Canada. Pierre.H.Vachon@Usherbrooke.ca
Harnois
Charlène
C
Grenier
Amélie
A
Dufour
Geneviève
G
Bouchard
Véronique
V
Han
Jiahuai
J
Landry
Jacques
J
Beaulieu
Jean-Fraçois
JF
Vézina
Anne
A
Dydensborg
Anders Bondo
AB
Gauthier
Rémy
R
Côté
André
A
Drolet
Jean-Fraçois
JF
Lareau
Fraçois
F
D023102:Anoikis / Q000502:physiology*; D018938:Caco-2 Cells; D002454:Cell Differentiation / Q000502:physiology; D020895:Enterocytes / Q000166:cytology / Q000502:physiology; D004789:Enzyme Activation / Q000502:physiology; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology* / Q000201:enzymology*; D007527:Isoenzymes / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D020033:Protein Isoforms / Q000502:physiology; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases
D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D007527:Isoenzymes; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D020033:Protein Isoforms; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases; C496050:PTK2 protein, human; C494918:AKT1 protein, human