Human intestinal epithelial cell survival and anoikis. Differentiation state-distinct regulation and roles of protein kinase B/Akt isoforms.
We have shown previously that human intestinal epithelial cell survival and anoikis are distinctively regulated according to the state of differentiation. Here we analyzed the roles of protein kinase B/Akt isoforms in such differentiation state distinctions. Anoikis was induced in undifferentiated and differentiated enterocytes by inhibition of focal adhesion kinase (Fak; pharmacologic inhibition or overexpression of dominant-negative mutants) or beta1 integrins (antibody blocking) or by maintaining cells in suspension. Expression/activation parameters of Akt isoforms (Akt-1, Akt-2, and Akt-3) and Fak were analyzed. Activity of Akt isoforms was also blocked by inhibition of phosphatidylinositol 3-kinase or by overexpression of dominant-negative mutants. Here we report the following. 1) The expression/activation levels of Akt-1 increase overall during enterocytic differentiation, and those of Akt-2 decrease, whereas Akt-3 is not expressed. 2) Akt-1 activation is dependent on beta1 integrins/Fak signaling, regardless of the differentiation state. 3) Akt-2 activation is dependent on beta1 integrins/Fak signaling in undifferentiated cells only. 4) Activation of Akt-1 is phosphatidylinositol 3-kinase-dependent, whereas that of Akt-2 is not. 5) Akt-2 does not promote survival or apoptosis/anoikis. 6) Akt-1 is essential for survival. 7) Akt-2 cannot substitute for Akt-1 in the suppression of anoikis. Hence, the expression and regulation of Akt isoforms show differentiation state-specific distinctions that ultimately reflect upon their selective implication in the mediation of human intestinal epithelial cell survival. These data provide new insights into the synchronized regulation of cell survival/death that is required in the dynamic renewal process of tissues such as the intestinal epithelium.
Canadian Institutes of Health Research Group on the Functional Development and Physiopathology of the Digestive Tract, Département d'Anatomie et de Biologie Cellulaire, Faculté de Médecine, Université de Sherbrooke, Québec J1H 5N4.
Geneviève
G
Dufour
Marie-Josée
MJ
Demers
David
D
Gagné
Anders Bondo
AB
Dydensborg
Inga C
IC
Teller
Véronique
V
Bouchard
Isabelle
I
Degongre
Jean-François
JF
Beaulieu
Jin Q
JQ
Cheng
Naoya
N
Fujita
Takashi
T
Tsuruo
Karine
K
Vallée
Pierre H
PH
Vachon
D023102:Anoikis / Q000187:drug effects / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology*; D002867:Chromones / Q000494:pharmacology; D015638:Cytochalasin D / Q000494:pharmacology; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology* / Q000502:physiology; D007527:Isoenzymes / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt
D002867:Chromones; D007527:Isoenzymes; D009025:Morpholines; D011518:Proto-Oncogene Proteins; D015638:Cytochalasin D; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D011505:Protein-Tyrosine Kinases; C494918:AKT1 protein, human; C494921:AKT2 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt