Calcitonin gene-related peptide (CGRP) increases intracellular free Ca2+ concentrations but not cyclic AMP formation in CGRP receptor-positive osteosarcoma cells (OHS-4).
Although calcitonin gene-related peptide (CGRP) may act as a local factor in bone, its mechanisms of action on osteoblasts are not well understood. We previously showed the presence of CGRP transcripts and peptide in human OHS-4 osteoblastic cells. The authors investigated the expression of CGRP receptor (CGRP-R) and its intracellular signalling properties in OHS-4 cells. Semi-quantitative RT-PCR analysis showed that OHS-4 cells express much more CGRP-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. Biochemical analysis showed that hCGRP did not increase intracellular cAMP levels in synchronized OHS-4 cells whatever was the cell cycle position. However, adenylate cyclase activity was functional, as human parathyroid hormone increased cAMP levels. In contrast, hCGRP induced a rapid, transient and dose-dependent increase in free cytosolic calcium levels. The data show that CGRP increases intracellular free Ca2+concentration but is not coupled to adenylate cyclase in CGRP receptor-positive OHS-4 osteosarcoma cells, suggesting that CGRP induces downstream events driven by phospholipase C in these cells.
Drissi
H
H
INSERM U 349, Lariboisière Hospital, Paris, France.
Lieberherr
M
M
Hott
M
M
Marie
P J
PJ
Lasmoles
F
F
D000818:Animals; D001483:Base Sequence; D002116:Calcitonin / Q000494:pharmacology; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000096:biosynthesis*; D017931:DNA Primers / Q000235:genetics; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism; D012516:Osteosarcoma / Q000235:genetics / Q000378:metabolism*; D018003:Receptors, Calcitonin / Q000235:genetics / Q000378:metabolism; D018015:Receptors, Calcitonin Gene-Related Peptide / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
D017931:DNA Primers; D018003:Receptors, Calcitonin; D018015:Receptors, Calcitonin Gene-Related Peptide; C028815:salmon calcitonin; D002116:Calcitonin; D000242:Cyclic AMP; D015740:Calcitonin Gene-Related Peptide; D002118:Calcium