Andress D L, Loop S M, Zapf J, Kiefer M C
Research Service, Veterans Affairs Medical Centers, Seattle, Washington 98108.
Biochem Biophys Res Commun. 1993 Aug 31;195(1):25-30. doi: 10.1006/bbrc.1993.2004.
Recently we demonstrated that a 23 kDa form of IGFBP-5, derived from osteoblast-like cells, stimulates osteoblast mitogenesis and enhances IGF-I action. Because osteoblast-derived IGFBP-5 is smaller than recombinant intact IGFBP-5 (23 vs 30 kDa) and has decreased binding affinity for IGF-I, we proposed that the native 23 kDa form of IGFBP-5 was truncated at a carboxy-terminal position. We now show that a recombinant form of carboxy-truncated IGFBP-5 binds IGF-I with reduced affinity and stimulates mitogenesis in mouse osteoblasts. We also show that 125I-truncated IGFBP-5 specifically binds to osteoblast monolayers with low binding affinity, similar to that seen with native 23 kDa IGFBP-5. These data indicate that carboxy-truncated IGFBP-5 stimulates osteoblast mitogenesis and suggest that reduced IGF-binding and cell-surface attachment are local mediators of this response.
最近我们证明，源自成骨样细胞的23 kDa形式的IGFBP-5可刺激成骨细胞有丝分裂并增强IGF-I的作用。由于成骨细胞来源的IGFBP-5比重组完整IGFBP-5小（23 kDa对30 kDa），且对IGF-I的结合亲和力降低，我们推测天然的23 kDa形式的IGFBP-5在羧基末端位置被截断。我们现在表明，羧基截断的IGFBP-5重组形式与IGF-I的结合亲和力降低，并刺激小鼠成骨细胞的有丝分裂。我们还表明，125I-截断的IGFBP-5以低结合亲和力特异性结合成骨细胞单层，类似于天然23 kDa IGFBP-5的情况。这些数据表明羧基截断的IGFBP-5刺激成骨细胞有丝分裂，并表明IGF结合和细胞表面附着的减少是这种反应的局部介质。
