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Identification of functional insulin‐like growth factor‐II/mannose‐6‐phosphate receptors in isolated bone cells
Author(s) -
Martinez D. A.,
Zuscik M. J.,
Ishibe M.,
Rosier R. N.,
Romano P. R.,
Cushing J. E.,
Puzas J. E.
Publication year - 1995
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.240590213
Subject(s) - mannose 6 phosphate , mannose , receptor , growth factor , identification (biology) , insulin like growth factor , microbiology and biotechnology , chemistry , endocrinology , biology , medicine , biochemistry , botany
The role of the IGF‐II/cation independent mannose‐6‐phosphate (IGF‐II/M6P) receptor in the transduction of cellular effects evoked by IGF‐II has been extensively debated in the literature. Many reports suggest that IGF‐II transduces its effects through the IGF‐I receptor, while others show that IGF‐II utilizes the type II receptor to affect cellular activity. This study (1) verifies the presence of the IGF‐II/M6P receptor in rat calvarial osteoblasts, and (2) evaluates the ability of the receptor to initiate intracellular single. Using conventional receptor binding assays, it was found that osteoblasts bind IGF‐II with high affinity. Scatchard analyses indicated that there are 5.08 × 10 4 IGF‐II/M6P receptor per osteoblast with a K d near (2.0 nM). The receptor protein was further identified by cross‐linking with 125 I‐IGF‐II. Northern analysis was used to identify an mRNA transcript for the IGF‐II/M6P receptor protein. To examine if the IGF‐II/M6P receptor can initiate second messenger signals, the ability of IGF‐II to evoke Ca 2+ transients was evaluated. Osteoblasts pretreated with IGF‐I did not lose their ability to respond to IGF‐II. Further, a polyclonal antibody against the rat IGF‐II/M6P receptor (R‐II‐PAB1) (1) was able to evoke its own Ca 2+ response, and (2) was able to block the generation of Ca 2+ transients caused by IGF‐II. The data in this report show that the osteoblastic Ca 2+ response to IGF‐II appears to be caused by an intracellular release of Ca 2+ which is mediated by the IGF‐II/M6P receptor making it possible to envision how the receptor may be an important modulator of osteoblast mediated osteogenesis. © 1995 Wiley‐Liss, Inc.