H. Drissi et al., Calcitonin gene-related peptide (CGRP) increases intracellular free Ca2+ concentrations but not cyclic AMP formation in CGRP receptor-positive osteosarcoma cells (OHS-4), CYTOKINE, 11(3), 1999, pp. 200-207
Although calcitonin gene-related peptide (CGRP) ma! act as a local factor i
n bone, its mechanisms of action an osteoblasts are not well understood. We
previously showed the presence of CGRP transcripts and peptide in human OH
S-4 osteoblastic cells, The authors investigated the expression of CGRP rec
eptor (CGRP-R) and its intracellular signalling properties in OHS-4 cells.
Semi-quantitative RT-PCR analysis showed that OHS-4 cells express much more
CC;RP-R than calcitonin (CT)-R transcripts. After amplification of CGRP-R
by RT-PCR and cloning of amplified fragments, the predicted CGRP-R sequence
in OHS-4 cells was found to share 100% identity with human lung CGRP-R, Bi
ochemical analysis showed that hCGRP did not increase intracellular cAMP le
vels in synchronized OHS-4 cells whatever was the cell cycle position. Howe
ver, adenylate cyclase activity nas functional, as human parathyroid hormon
e increased cAMP levels. In contrast, hCGRP induced a rapid, transient and
dose-dependent increase in free cytosolic calcium levels. The data show tha
t CGRP increases intracellular free Ca2+ concentration but is not coupled t
o adenylate cyclase in CGRP receptor-positive OHS-4 osteosarcoma cells, sug
gesting that CGRP induces downstream events driven by phospholipase C in th
ese cells. (C) 1999 Academic Press.