Identification of STAT-1 as a molecular target of IGFBP-3 in the process of chondrogenesis

Anna Spagnoli, Monica Torello, Srivinasa R. Nagalla, William A. Horton, Patrick Pattee, Vivian Hwa, Francesco Chiarelli, Charles T. Roberts, Ron G. Rosenfeld

Research output: Contribution to journalArticlepeer-review

44 Scopus citations


The chondrogenesis process requires the ordered proliferation and differentiation of chondrocytes. Insulin-like growth factor-binding protein (IGFBP)-3, well characterized as the carrier of insulin-like growth factor (IGF), has been reported to have intrinsic bioactivity that is independent of IGF binding. The mechanisms involved in this IGF-independent action are still unclear. Using the RCJ3.1C5.18 chondrogenic cells, which in culture progresses from undifferentiated to terminally differentiated chondrocytes, we have shown previously that IGFBP-3 has an IGF-independent, antiproliferative effect in undifferentiated and early differentiated but not in terminally differentiated chondrocytes. In the present study, cDNA microarray analysis was used to screen for genes: 1) that were regulated by IGFBP-3 in early but not in terminally differentiated chondrocytes; 2) that were regulated specifically by IGFBP-3, but not by IGF-I; and 3) whose regulation was abolished by coincubation of IG-FBP-3 with IGF-I. Signal transducer and activator of transcription (STAT)-I was the gene that, fulfilling the screening criteria, exhibited the greatest up-regulation by IGFBP-3 (>40-fold). STAT-1 gene up-regulation was confirmed by Northern analysis of cells treated with IGFBP-3 or transfected with an IGFBP-3 expression vector. Remarkably, similar results were obtained when cells were transfected with an IGFBP-3 mutant unable to bind IGFs, definitively demonstrating the IGF-independent action of IGFBP-3. Consistent with the up-regulation of STAT-1 mRNA, IGFBP-3 also increased STAT-1 protein expression. Furthermore, both IGFBP-3 and the IGFBP-3 mutant induced STAT-1 phosphorylation and its nuclear localization. An antisense STAT-1 oligonucleotide abolished the IGF-independent cell apoptosis induced by IGFBP-3. We have demonstrated that STAT-1 is a major intracellular signaling and transcriptional target of the IGF-independent apoptotic effect of IGFBP-3 in chondrogenesis.

Original languageEnglish (US)
Pages (from-to)18860-18867
Number of pages8
JournalJournal of Biological Chemistry
Issue number21
StatePublished - May 24 2002
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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