Role of the IGF-II receptor in mediating acute, non-genomic effects of retinoids and IGF-II on keratinocyte cell death.
In this study, we have examined the effects of retinoic acid (RA) on the human immortalized keratinocyte cell line (HaCaT). A significant twofold (P < 0.01) increase in apoptotic cell death compared with the control was found within 24 h of treatment with 10-5 M of RA. Apoptosis was confirmed by flow cytometry. Cycloheximide did not inhibit this acute RA-induced apoptosis. Interestingly, insulin-like growth factor-II (IGF-II, 50 ng/ml) was able to significantly (67.3%; P < 0.05) reduce RA effects, whereas IGF-I (50 ng/ml) and insulin (75 ng/ml) were without effect. Furthermore, analogues of IGF-II [leu27 IGF-II and Des(1-6) IGF-II], with altered affinities for the IGF-I receptor and IGF-binding proteins (IGFBPs), but retained affinities for the IGF-II receptor, also completely inhibited (100%; P < 0.01) RA-induced apoptosis, while an IGF-I receptor antagonist did not reduce the survival effects of IGF-II. Insulin pretreatment negates the survival effect of IGF-II. In contrast, mannose 6 phosphate (M6P) did not alter RA or IGF-II actions. These results indicate that rapid induction of cell death by RA is independent of production or secretion of new proteins. The inhibition of RA action by IGF-II was independent of its ability to signal through the IGF-I receptor or to interact with IGFBPs.
Louafi
F
F
Division of Surgery, Bristol Royal Infirmary, Bristol, United Kingdom.
Stewart
C E H
CE
Perks
C M
CM
Thomas
M G
MG
Holly
J M P
JM
D017209:Apoptosis / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology*; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D008360:Mannosephosphates / Q000494:pharmacology; D017526:Receptor, IGF Type 1 / Q000187:drug effects / Q000378:metabolism; D017527:Receptor, IGF Type 2 / Q000187:drug effects / Q000378:metabolism*; D011994:Recombinant Proteins / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology*
D007328:Insulin; D008360:Mannosephosphates; D017527:Receptor, IGF Type 2; D011994:Recombinant Proteins; C027693:mannose-6-phosphate; D014212:Tretinoin; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D003513:Cycloheximide; D017526:Receptor, IGF Type 1