Insulin-like growth factors I and II are autocrine factors in stimulating proteoglycan synthesis, a marker of differentiated chondrocytes, acting through their respective receptors on a clonal human chondrosarcoma-derived chondrocyte cell line, HCS-2/8. 1997

M Takigawa, and T Okawa, and H Pan, and C Aoki, and K Takahashi, and J Zue, and F Suzuki, and A Kinoshita
Department of Biochemistry and Molecular Dentistry, Okayama University Dental School, Japan. takigawa@dent.okayama-u.ac.jp

Both insulin-like growth factor (IGF)-I and IGF-II increased the synthesis of cartilage-type, large proteoglycan in a human chondrosarcoma-derived chondrocyte cell line, HCS-2/8. In contrast to the stimulatory effects of IGFs on costal chondrocytes of the young rabbit, the stimulatory effect of IGF-II on proteoglycan synthesis in HCS-2/8 cells was more potent than that of IGF-I. IGF-II, but not IGF-I, increased calcium influx into HCS-2/8 cells, and there was a close relation between the stimulation of proteoglycan synthesis and the calcium influx. [125I]IGF-I bound to HCS-2/8 cells, and this binding was competitively inhibited by low concentrations of unlabeled IGF-I, higher concentrations of IGF-II, and much higher concentrations of insulin. [125I]IGF-II also bound to the cells, and its binding was competitively inhibited by IGF-II and slightly inhibited by higher concentrations of IGF-I and much higher concentrations of insulin. When radioligand-receptor complexes were separated by SDS-PAGE and subjected to autoradiography, two major bands at 260 and 130 kDa were observed, which correspond to the IGF type II receptor (IGF-IIR) and the alpha subunit of the IGF type I receptor (IGF-IR), indicating the presence of both receptors. When confluent cultures of HCS-2/8 cells were maintained in serum-free medium, proteoglycan synthesis did not decrease unless the medium was repeatedly replaced. Conditioned medium of HCS-2/8 cells stimulated the HCS-2/8 cells to synthesize proteoglycans. RIA revealed that the cells produced both IGF-II and IGF-I. Transcripts of messenger RNAs of both IGF-I and IGF-II and both IGF-IR and IGF-IIR also were detectable by Northern analysis. Both anti-IGF-IR antibody and anti-IGF-II antibody inhibited proteoglycan synthesis. Mannose-6-phosphate, which is known to bind to IGF-IIR, stimulated proteoglycan synthesis, potentiated IGF-II-stimulated proteoglycan synthesis, and enhanced the binding affinity for IGF-II but not for IGF-I. Even in the presence of anti-IGF-IR antibody, IGF-II and mannose-6-phosphate stimulated proteoglycan synthesis in the cells. [Leu27]IGF-II, an IGF-II analogue with high affinity only for IGF-IIR, strongly stimulated proteoglycan synthesis in HCS-2/8 cells but [Arg54, Arg55]IGF-II, which binds to only IGF-IR, also stimulated proteoglycan synthesis in the cells. These findings indicate that IGF-I and IGF-II act as autocrine differentiation factors for this chondrocytic permanent cell line, HCS-2/8, mainly via respective receptors.

UI MeSH Term Description Entries
D007334 Insulin-Like Growth Factor I A well-characterized basic peptide believed to be secreted by the liver and to circulate in the blood. It has growth-regulating, insulin-like, and mitogenic activities. This growth factor has a major, but not absolute, dependence on GROWTH HORMONE. It is believed to be mainly active in adults in contrast to INSULIN-LIKE GROWTH FACTOR II, which is a major fetal growth factor. IGF-I,Somatomedin C,IGF-1,IGF-I-SmC,Insulin Like Growth Factor I,Insulin-Like Somatomedin Peptide I,Insulin Like Somatomedin Peptide I
D007335 Insulin-Like Growth Factor II A well-characterized neutral peptide believed to be secreted by the LIVER and to circulate in the BLOOD. It has growth-regulating, insulin-like and mitogenic activities. The growth factor has a major, but not absolute, dependence on SOMATOTROPIN. It is believed to be a major fetal growth factor in contrast to INSULIN-LIKE GROWTH FACTOR I, which is a major growth factor in adults. IGF-II,Multiplication-Stimulating Activity,Somatomedin MSA,IGF-2,Insulin Like Growth Factor II,Insulin-Like Somatomedin Peptide II,Multiplication-Stimulating Factor,Somatomedin A,Factor, Multiplication-Stimulating,Insulin Like Somatomedin Peptide II,Multiplication Stimulating Activity,Multiplication Stimulating Factor
D007457 Iodine Radioisotopes Unstable isotopes of iodine that decay or disintegrate emitting radiation. I atoms with atomic weights 117-139, except I 127, are radioactive iodine isotopes. Radioisotopes, Iodine
D008297 Male Males
D008360 Mannosephosphates Phosphoric acid esters of mannose.
D011485 Protein Binding The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments. Plasma Protein Binding Capacity,Binding, Protein
D011509 Proteoglycans Glycoproteins which have a very high polysaccharide content. Proteoglycan,Proteoglycan Type H
D011817 Rabbits A burrowing plant-eating mammal with hind limbs that are longer than its fore limbs. It belongs to the family Leporidae of the order Lagomorpha, and in contrast to hares, possesses 22 instead of 24 pairs of chromosomes. Belgian Hare,New Zealand Rabbit,New Zealand Rabbits,New Zealand White Rabbit,Rabbit,Rabbit, Domestic,Chinchilla Rabbits,NZW Rabbits,New Zealand White Rabbits,Oryctolagus cuniculus,Chinchilla Rabbit,Domestic Rabbit,Domestic Rabbits,Hare, Belgian,NZW Rabbit,Rabbit, Chinchilla,Rabbit, NZW,Rabbit, New Zealand,Rabbits, Chinchilla,Rabbits, Domestic,Rabbits, NZW,Rabbits, New Zealand,Zealand Rabbit, New,Zealand Rabbits, New,cuniculus, Oryctolagus
D001859 Bone Neoplasms Tumors or cancer located in bone tissue or specific BONES. Bone Cancer,Cancer of Bone,Cancer of the Bone,Neoplasms, Bone,Bone Neoplasm,Neoplasm, Bone
D002118 Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation

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