Journal of Clinical Endocrinology & Metabolism, Vol 77, 1125-1129, Copyright © 1993 by Endocrine Society

ARTICLES

Invasive human pituitary tumors express a point-mutated alpha-protein kinase-C

V Alvaro, L Levy, C Dubray, A Roche, F Peillon, B Querat and D Joubert
Centre CNRS-INSERM de Pharmacologie et d'Endocrinologie, Montpellier, France.

Protein kinase-C (PKC) is a ubiquitous eukaryotic kinase that plays a key role in transmembrane signaling and influences important cellular processes, such as proliferation. Increases in its activity and expression have been demonstrated in adenomatous human pituitaries, with protein expression being the highest in invasive tumors (1). Moreover, in these same invasive tumors, the mean increase in expression (8.9-fold) does not correlate with the mean increase in activity (2.6-fold), suggesting a dysfunction in PKC in these tumors. Here, we show that the PKC alpha-isoform (alpha PKC) is overexpressed in human pituitary tumors. The complete sequencing of the PKC cDNA from four invasive tumors has revealed a point mutation that is absent in the noninvasive tumors analyzed. The point mutation is located at position 294 of the protein, in the V3 region, leading to a substitution of a negatively charged aspartic acid by an apolar glycine. Thus, not only is alpha PKC overexpressed in human pituitary tumors, but it is also structurally altered in the invasive subpopulation of these tumors.

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