The mitogenic effects of the B beta chain of fibrinogen are mediated through cell surface calreticulin.
We have previously shown that soluble partially degraded fibrin(ogen) remains in solution after fibrin clot formation and is a potent fibroblast mitogen (Gray, A.J., Bishop, J.E., Reeves J.T., Mecham, R.P., and Laurent, G.J. (1995) Am. J. Cell Mol. Biol. 12, 684-690). Mitogenic sites within the fibrin(ogen) molecule are located on the A alpha and B beta chains of the protein (Gray, A.J., Bishop, J. E., Reeves, J.T., and Laurent, G.J. (1993) J. Cell Sci. 104, 409-413). However, receptor pathways through which mitogenic effects are mediated are unknown. The present study sought to determine the nature of fibrin(ogen) receptors expressed on human fibroblasts which interact with the fibrinogen B beta chain. Receptor complexes were isolated from 125I-surface-labeled fibroblasts and purified on a fibrinogen B beta chain affinity column. Subsequent high performance liquid chromatography and SDS-polyacrylamide gel electrophoresis analysis indicated fibrinogen B beta chain bound specifically to a 60-kDa surface protein. Sequence analysis of the amino terminus of this protein indicated 100% homology to human calreticulin. Immunoprecipitation experiments employing a polyclonal anti-calreticulin antibody provided further evidence that the 60-kDa protein isolated in this study was calreticulin. Further, polyclonal antibodies to human calreticulin significantly inhibited the mitogenic activity of fibrinogen B beta chain on human fibroblasts. The present study has shown that cell surface calreticulin binds to the B beta chain of fibrinogen mediating its mitogenic activity.
Gray
A J
AJ
University College London Medical School, Division of Cardiopulmonary Biochemistry, United Kingdom.
Park
P W
PW
Broekelmann
T J
TJ
Laurent
G J
GJ
Reeves
J T
JT
Stenmark
K R
KR
Mecham
R P
RP
D000595:Amino Acid Sequence; D000906:Antibodies / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D037282:Calreticulin; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D005340:Fibrinogen / Q000378:metabolism* / Q000494:pharmacology*; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D037102:Lectins / Q000378:metabolism; D008168:Lung; D046911:Macromolecular Substances; D008934:Mitogens / Q000494:pharmacology*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D012261:Ribonucleoproteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
D000906:Antibodies; D002135:Calcium-Binding Proteins; D037282:Calreticulin; D037102:Lectins; D046911:Macromolecular Substances; D008934:Mitogens; D010446:Peptide Fragments; D012261:Ribonucleoproteins; D005340:Fibrinogen