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Evidence for an Insulin‐Like Growth Factor Autocrine‐Paracrine System in the Retinal Photoreceptor‐Pigment Epithelial Cell Complex
Author(s) -
Waldbillig Robert J.,
Pfeffer Bruce A.,
Schoen Timothy J.,
Adler Alice A.,
ShenOrr Z.,
Scavo Louis,
ERoith Derek,
Chader Gerald J.
Publication year - 1991
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1991.tb06347.x
Subject(s) - autocrine signalling , paracrine signalling , retinal , growth factor , microbiology and biotechnology , biology , receptor , retina , insulin like growth factor , retinal pigment epithelium , immunoprecipitation , biochemistry , neuroscience , gene
: The interphotoreceptor matrix (IPM), lying between retinal photoreceptor and pigment epithelial (RPE) cells, contains insulin‐like growth factor I (IGF‐I) immunoreactivity that co‐elutes with authentic human IGF‐I in HPLC analyses. Cultured human RPE cells synthesize and release IGF‐I, raising the possibility that the RPE serves as a source of IPM IGF‐I in vivo. Photoreceptor rod outer segments and cultured monkey RPE cells express specific IGF‐I receptors with α‐subunits of 120 and 138 kDa, respectively. They thus appear to be of the “brain” (in photoreceptors) and “peripheral” (in RPE cells) receptor subtypes. Additionally, the IPM contains high levels of an IGF binding protein (IGF‐BP) that specifically binds IGF‐I and IGF‐II. The IPM‐BP is visualized as a single radiographic band by both ligand blot and affinity cross‐linking procedures. With enzymes specific for removing N‐and O‐linked oligosaccharides, the IPM‐BP was found to contain O‐but not N‐linked glycosylated side chains. The distinctive size and glycosylation pattern of the IPM‐BP indicate that it is not derived from the vitreous or serum but instead is synthesized locally. The presence of IGF‐I and IGF‐BP in the IPM, together with the presence of IGF‐I receptors on both photoreceptor and RPE cells, suggests the presence of an outer retina autocrine‐paracrine system.