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Guanine Nucleotide Regulatory Proteins, G q and G i1/2 , Mediate Platelet‐Activating Factor‐Stimulated Phosphoinositide Metabolism in Immortalized Hippocampal Cells
Author(s) -
Shi LengChu,
Wang HoauYan,
Horwitz Joel,
Friedman Eitan
Publication year - 1996
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 - 10.1046/j.1471-4159.1996.67041478.x
Subject(s) - platelet activating factor , g protein , pertussis toxin , biology , platelet activating factor receptor , receptor , hippocampal formation , stimulation , microbiology and biotechnology , biochemistry , endocrinology , antagonist , medicine
Platelet‐activating factor (PAF) may be a neuromodulator involved in neural cell differentiation, cerebral inflammation, and ischemia. The PAF receptor is a member of the G protein‐coupled receptor superfamily. In the present study, we sought to define the specific G protein(s) that mediate PAF‐stimulated phosphoinositide (PI) metabolism in an immortalized hippocampal cell line, HN33.11. PAF increased the production of 3 H‐labeled inositol phosphates (IPs) with EC 50 values of 1.2–1.5 n M . The effect of PAF on 3 H‐IPs formation was completely blocked by the PAF antagonist BN 50739 at a concentration of 300 n M . Pertussis toxin pretreatment attenuated PAF‐stimulated 3 H‐IPs production by 20–30% ( p < 0.05). Consistent with a role for G i1/2 in this response, antiserum against G αi1/2 blocked the response to a similar degree. Pretreatment of permeabilized cells with G αq/11 antiserum attenuated the response by 70% ( p < 0.05), suggesting a role for G q/11 in mediating the PAF response in this cell line. Stimulation with PAF increased [α‐ 32 P]‐GTP binding to both G αq and G αi1/2 proteins. Moreover, specific [ 3 H]PAF binding sites coprecipitated with G αq and G αi1/2 proteins. The results suggest that PAF‐stimulated PI metabolism in HN33.11 cells is mediated by both G q and G i1/2 proteins.