Increased parathyroid hormone-related peptide (pthrp) production by
a tyrosine kinase oncogene, tpr-met: role of the ras signalling
pathway.
Aklilu, F., M. Park, D. Goltzman, S. A. Rabbani.
Department of Medicine, McGill University and Calcium Research
Laboratory and MolecularOncology Group, Royal Victoria Hospital,
Montreal, Canada H3A 1A1
APStracts 3:0072E, 1996.
We have used the Tpr-Met oncogene as a model to examine signalling
pathways of growth factors and tyrosine kinase oncogenes which can
increase parathyroid hormone-related peptide (PTHRP) production.
PTHRP production, in Tpr-Met transfected cells, when assessed by
Northern blot analysis and radioimmunoassay, was increased 4-8 fold.
Treatment of these cells with the transcriptional inhibitor,
actinomycin D, and nuclear run-off assays showed that the major cause
of increased PTHRP mRNA was enhanced gene transcription. To analyze
the intracellular signalling molecules involved in PTHRP production,
stable cell lines expressing a Tyr489 Phe mutant of the Tpr-Met
oncoprotein were examined. The mutant fails to activate
phosphatidylinositol (PI)-3 kinase or associate with the Grb-2
adaptor protein and caused a significant reduction in PTHRP
production. Treatment of wild-type Tpr-Met transfected cells with
wortmannin, a PI-3 kinase inhibitor, had no effect on PTHRP
production, however, treatment of these cells with lovastatin, an
inhibitor of p21ras isoprenylation, significantly reduced PTHRP
expression. These results show that PTHRP is a downsteam target of
the Tpr-Met oncogene and indicate that the PTHRP stimulating activity
is mediated via the Ras signalling pathway.
Received 28 December 1995; accepted in final form 18 March 1996.
APS Manuscript Number E607-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 1 April 96