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Am J Physiol Endocrinol Metab (November 19, 2002). doi:10.1152/ajpendo.00503.2001
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Articles in PresS, published online ahead of print November 19, 2002
Am J Physiol Endocrinol Metab, 10.1152/ajpendo.00503.2001
Submitted on November 7, 2001
Accepted on November 17, 2002

INSULIN MODULATES PC-1 PROCESSING AND RECRUITMENT IN CULTURED HUMAN CELLS

Claudia Menzaghi1*, Rosa Di Paola2, Germano Baj3, Ada Funaro4, Alberto Arnulfo3, Tonino Ercolino2, Nicola Surico5, Fabio Malavasi4, and Vincenzo Trischitta6

1 Lab of Immunogenetics, Department of Genetics, Biology and Biochemistry, University of Torino, Medical School, Torino, Italy; Unit of Endocrinology, Scientific Institute, San Giovanni Rotondo, Foggia, Italy
2 Unit of Endocrinology, Scientific Institute, San Giovanni Rotondo, Foggia, Italy
3 Lab of Immunogenetics, Department of Genetics, Biology and Biochemistry, University of Torino, Medical School, Torino, Italy; Division of Obstetrics and Gynecology, Department of Medical Science, University A. Avogadro of Eastern Piedmont, Novara, Italy
4 Lab of Immunogenetics, Department of Genetics, Biology and Biochemistry, University of Torino, Medical School, Torino, Italy; Experimental Medicine Center, University of Torino, Medical School, Torino, Italy
5 Division of Obstetrics and Gynecology, Department of Medical Science, University A. Avogadro of Eastern Piedmont, Novara, Italy
6 Unit of Endocrinology, Scientific Institute, San Giovanni Rotondo, Foggia, Italy; Department of Clinical Science, University of Rome, Roma, Italy

* To whom correspondence should be addressed. E-mail: endocrinologia{at}operapadrerpio.it.

We evaluated whether insulin signalling modulates PC-1 plasma membrane recruitment, post-translational processing and gene expression in human cultured cell lines. Insulin induced a 4-fold 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 PI3 kinase (200 nmol/l wortmannin), and S6 kinase (50 nmol/l rapamycin) activities and intracellular trafficking (50 µmol/l monensin) and 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 those of 163, 117, 106 and 97 kDa observed also in absence of insulin) which was sensitive to endoglycosidase H. Finally, inhibition of PC-1 translocation to plasma membrane, by wortmannin pre-treatment, increases insulin stimulated receptor autophosphorylation. Our data indicate insulin stimulates PC-1 post translational processing and translocation to plasma membrane, which, in turn, impairs insulin receptor signalling. A bi-directional cross-talk between insulin and PC-1, therefore, takes place, which may be part of the hormone self-desensitisation mechanism.






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