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Insulin‐like growth factor I in cultured rat astrocytes: expression of the gene, and receptor tyrosine kinase.
Author(s) -
Ballotti R.,
Nielsen F. C.,
Pringle N.,
Kowalski A.,
Richardson W. D.,
Van Obberghen E.,
Gammeltoft S.
Publication year - 1987
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1987.tb02695.x
Subject(s) - biology , receptor tyrosine kinase , insulin receptor , irs2 , tyrosine kinase , gene expression , insulin like growth factor , platelet derived growth factor receptor , tropomyosin receptor kinase c , growth factor , endocrinology , gene , microbiology and biotechnology , insulin , medicine , receptor , signal transduction , genetics , insulin resistance
Gene expression, receptor binding and growth‐promoting activity of insulin‐like growth factor I (IGF I) was studied in cultured astrocytes from developing rat brain. Northern blot analysis of poly(A)+ RNAs from astrocytes revealed an IGF I mRNA of 1.9 kb. Competitive binding and receptor labelling techniques revealed two types of IGF receptor in astroglial cells. Type I IGF receptors consist of alpha‐subunits (Mr 130,000) which bind IGF I with significantly higher affinity than IGF II, and beta‐subunits (Mr 94,000) which show IGF I‐sensitive tyrosine kinase activity. Type II IGF receptors are monomers (Mr 250,000) which bind IGF II with three times higher affinity than IGF I. Both types of IGF receptor recognize insulin weakly. DNA synthesis measured by cellular thymidine incorporation was stimulated 2‐fold by IGF I and IGF II. IGF I was more potent than IGF II, and both were significantly more potent than insulin. Our findings suggest that IGF I is synthesized in fetal rat astrocytes and acts as a growth promoter for the same cells by activation of the type I IGF receptor tyrosine kinase. We propose that IGF I acts through autocrine or paracrine mechanisms to stimulate astroglial cell growth during normal brain development.