Corticotropin-induced secreted protein, an ACTH-induced protein secreted by adrenocortical cells, is structurally related to thrombospondins.
The treatment of primary cultures of bovine adrenocortical cells with nanomolar concentrations of ACTH induces a 10-fold increase in the synthesis of a secreted protein of apparent molecular mass 195 kDa on reducing SDS-polyacrylamide gels. This corticotropin-induced secreted protein (CISP) appears to be an oligomeric calcium-binding protein. Its secretion under serum-free culture conditions is sustained over 4 days in the continuous presence of ACTH. Induction of CISP secretion by ACTH is mimicked by cAMP analogs and adenylate cyclase activators. We report here the purification of CISP to apparent homogeneity with an overall yield of 43% using a combination of heparin-agarose and Mono-Q chromatographies. The NH2-terminal amino acid sequence and the sequence of several tryptic peptides revealed that CISP is structurally related to the members of the thrombospondin (TSP) family. Among these members, bovine CISP appeared to be more homologous to mouse TSP2 (85% identity in the 29 amino acid long NH2-terminal sequence) than to TSP1 (18% identity in the same region). We also observed that CISP binds Ca2+ and is an adhesive protein for bovine adrenocortical cells. Thus, CISP possesses both structural and functional properties of thrombospondins. Whether CISP represents the bovine form of TSP2 or a novel member of the expanding thrombospondin family will need to be elucidated by cloning and sequencing of a larger portion of the molecule.
Institut National de la Santé et de la REcherche Médicale Unité 244, Departement de Biologie Moléculaire et Structurale, Grenoble, France.
S
S
Pellerin
B
B
Lafeuillade
N
N
Scherrer
J
J
Gagnon
D L
DL
Shi
E M
EM
Chambaz
J J
JJ
Feige
D000302:Adrenal Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000595:Amino Acid Sequence; D000818:Animals; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002417:Cattle; D015815:Cell Adhesion Molecules / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002478:Cells, Cultured; D002853:Chromatography, Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D008969:Molecular Sequence Data; D010980:Platelet Membrane Glycoproteins / Q000737:chemistry*; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D019699:Thrombospondins
D002135:Calcium-Binding Proteins; D015815:Cell Adhesion Molecules; D010980:Platelet Membrane Glycoproteins; D019699:Thrombospondins; C079864:corticotropin-induced secreted protein, Bos taurus; D000324:Adrenocorticotropic Hormone