Identification and cloning of a connective tissue growth factor-like cDNA from human osteoblasts encoding a novel regulator of osteoblast functions.
We have identified and cloned a novel connective tissue growth factor-like (CTGF-L) cDNA from primary human osteoblast cells encoding a 250-amino acid single chain polypeptide. Murine CTGF-L cDNA, encoding a polypeptide of 251 amino acids, was obtained from a murine lung cDNA library. CTGF-L protein bears significant identity ( approximately 60%) to the CCN (CTGF, Cef10/Cyr61, Nov) family of proteins. CTGF-L is composed of three distinct domains, an insulin-like growth factor binding domain, a von Willebrand Factor type C motif, and a thrombospondin type I repeat. However, unlike CTGF, CTGF-L lacks the C-terminal domain implicated in dimerization and heparin binding. CTGF-L mRNA ( approximately 1.3 kilobases) is expressed in primary human osteoblasts, fibroblasts, ovary, testes, and heart, and a approximately 26-kDa protein is secreted from primary human osteoblasts and fibroblasts. In situ hybridization indicates high expression in osteoblasts forming bone, discrete alkaline phosphatase positive bone marrow cells, and chondrocytes. Specific binding of 125I-labeled insulin-like growth factors to CTGF-L was demonstrated by ligand Western blotting and cross-linking experiments. Recombinant human CTGF-L promotes the adhesion of osteoblast cells and inhibits the binding of fibrinogen to integrin receptors. In addition, recombinant human CTGF-L inhibits osteocalcin production in rat osteoblast-like Ros 17/2.8 cells. Taken together, these results suggest that CTGF-L may play an important role in modulating bone turnover.
Kumar
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S
Department of Bone and Cartilage Biology, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406, USA. Sanjay_Kumar@sbphrd.com
Hand
A T
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Connor
J R
JR
Dodds
R A
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Ryan
P J
PJ
Trill
J J
JJ
Fisher
S M
SM
Nuttall
M E
ME
Lipshutz
D B
DB
Zou
C
C
Hwang
S M
SM
Votta
B J
BJ
James
I E
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Rieman
D J
DJ
Gowen
M
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Lee
J C
JC
D000595:Amino Acid Sequence; D000818:Animals; D001842:Bone and Bones / Q000378:metabolism*; D055511:CCN Intercellular Signaling Proteins; D002448:Cell Adhesion; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005340:Fibrinogen / Q000378:metabolism; D006133:Growth Substances / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins; D051379:Mice; D008969:Molecular Sequence Data; D005810:Multigene Family; D009363:Neoplasm Proteins; D010006:Osteoblasts / Q000378:metabolism*; D015675:Osteocalcin / Q000096:biosynthesis; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D019030:Receptors, Vitronectin / Q000378:metabolism; D012097:Repressor Proteins; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014157:Transcription Factors
D055511:CCN Intercellular Signaling Proteins; C413323:CCN5 protein, human; D018076:DNA, Complementary; D006133:Growth Substances; D036341:Intercellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D019030:Receptors, Vitronectin; D012097:Repressor Proteins; D014157:Transcription Factors; D015675:Osteocalcin; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D005340:Fibrinogen