Reduced insulin receptor expression and function in human colonic Caco-2 cells by ras and polyoma middle T oncogenes.
Taking advantage of the potent mitogenic effect exerted by insulin in human colonic cells, we used Caco-2 cells transfected with an activated (Val-12) human Haras gene or the polyoma middle T (PyMT) oncogene, a constitutive activator of pp60c-src tyrosine kinase activity, to investigate the effect of oncogenic p21ras and PyMT/pp60c-src on insulin mitogenic signaling. As compared to vector control Caco-2 cells, both oncogene-transfected cells exhibited: 1) a loss of response to insulin's stimulatory effect on mitogen-activated protein (MAP) kinase activity and cell proliferation, both of which were constitutively increased; 2) a decrease in insulin receptor (IR) affinity and insulin-stimulated exogenous tyrosine kinase activity, which resulted from increased protein kinase C (PKC) activity (Delage, S., Chastre, E., Empereur, S., Wicek, D., Veissiére, D., Capeau, J., Gespach, C., and Cherqui, G. (1993) Cancer Res. 53, 2762-2770), since IR alterations were corrected by PKC down-regulation; and 3) a decrease in both IR mRNA level and IR number, which was independent of PKC since it persisted after PKC down-regulation. In conclusion, this is the first evidence that oncogenic p21ras and PyMT/pp60c-src abolish insulin mitogenic signaling in human colonic cells through mechanisms involving (i) constitutive activation of MAP kinase and (ii) marked decreases in both IR function and expression which are mediated by PKC-dependent and PKC-independent pathways, respectively.
Laboratoire de Biologie Cellulaire, INSERM U.402, Faculté de Médecine Saint-Antoine, Paris, France.
S
S
Baron-Delage
J
J
Capeau
V
V
Barbu
E
E
Chastre
P
P
Levy
C
C
Gespach
G
G
Cherqui
D000952:Antigens, Polyomavirus Transforming / Q000235:genetics*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D003110:Colonic Neoplasms; D004261:DNA Replication / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D011905:Genes, ras; D006801:Humans; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D009857:Oncogenes; D011493:Protein Kinase C / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011972:Receptor, Insulin / Q000096:biosynthesis / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
D000952:Antigens, Polyomavirus Transforming; D007328:Insulin; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D011972:Receptor, Insulin; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D013936:Thymidine