AJP - Cell Physiology, Vol 265, Issue 5 C1289-C1297, Copyright © 1993 by American Physiological Society
Immediate cell signal by bone-related peptides in human osteoclast-like cells
R. Paniccia, S. Colucci, M. Grano, M. Serra, A. Z. Zallone and A. Teti
Institute of Human Anatomy, School of Pharmacy, University of Bari, Italy.
We tested whether recognition of bone-related peptides regulates
intracellular Ca2+ concentration ([Ca2+]i) of giant cell tumor of bone
(GCT). [Ca2+]i was measured in single cells by fura 2 fluorometry. GCT
cells were sensitive to bone sialoprotein-II (BSP-II), osteopontin (OPN),
and related fragments. Responses consisted of a prompt increase of [Ca2+]i,
mostly transient, with a peak followed by a rapid return toward baseline.
Responses were not mimicked by bovine plasma fibronectin. Sensitivity of
GCT cells to bone peptides was specific, since BALB/3T3 fibroblasts and
U-937 histiocytic lymphoma cells with monocytic phenotype failed to respond
to BSP-II and OPN fragments. GRGDSP synthetic esapeptide, carrying the
Arg-Gly-Asp adhesive motif, and GRGESP (Asp replaced by Glu), but not the
GRADSP (Gly replaced by Ala), were active in inducing [Ca2+]i transients as
well. Responses were observed also in cells treated with the BSP-II 1C
fragment, lacking any known adhesive sequence, indicating that the active
peptides inducing [Ca2+]i increments may be multiple. Sensitivity to
extracellular matrix peptides was present in a variable fraction of the
cells and was downregulated on long-term culture. The mechanism inducing
[Ca2+]i elevations was mostly related to Ca2+ release from
thapsigargin-sensitive intracellular pools.
