Insulin modulates PC-1 processing and recruitment in cultured human cells.
We evaluated whether insulin signaling modulates plasma cell glycoprotein (PC-1) plasma membrane recruitment, posttranslational processing, and gene expression in human cultured cell lines. Insulin induced a fourfold increase (P < 0.01) of membrane PC-1 expression by rapid and sensitive mechanism(s). This effect was reduced (P < 0.05-0.01) by inhibition of phosphatidylinositol 3-kinase (200 nmol/l wortmannin) and S6 kinase (50 nmol/l rapamycin) activities and intracellular trafficking (50 micromol/l monensin) and was not accompanied by PC-1 gene expression changes. Moreover, at Western blot, insulin elicited the appearance, in both plasma membrane and cytosol, of a PC-1-related 146-kDa band (in addition to bands of 163, 117, 106, and 97 kDa observed also in absence of insulin) that was sensitive to endoglycosidase H. Finally, inhibition of PC-1 translocation to plasma membrane, by wortmannin pretreatment, increases insulin-stimulated receptor autophosphorylation. Our data indicate that insulin stimulates PC-1 posttranslational processing and translocation to the plasma membrane, which in turn impairs insulin receptor signaling. Bidirectional cross talk between insulin and PC-1, therefore, takes place, which may be part of the hormone self-desensitization mechanism.
Menzaghi
C
C
Laboratory of Immunogenetics, Department of Genetics, Biology and Biochemistry, University of Torino Medical School, Italy. endocrinologia@operapadrepio.it
Di Paola
R
R
Baj
G
G
Funaro
A
A
Arnulfo
A
A
Ercolino
T
T
Surico
N
N
Malavasi
F
F
Trischitta
V
V
D000730:Androstadienes / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002462:Cell Membrane / Q000502:physiology; D003600:Cytosol / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007328:Insulin / Q000494:pharmacology / Q000502:physiology*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010727:Phosphoric Diester Hydrolases / Q000737:chemistry / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational; D011755:Pyrophosphatases / Q000737:chemistry / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014407:Tumor Cells, Cultured; D000077191:Wortmannin
D000730:Androstadienes; D007328:Insulin; D010726:Phosphodiesterase Inhibitors; D011956:Receptors, Cell Surface; D010727:Phosphoric Diester Hydrolases; C065962:ectonucleotide pyrophosphatase phosphodiesterase 1; D011755:Pyrophosphatases; D000077191:Wortmannin