Preparation of functional human lysophosphatidic acid receptor 2 using a P9 ∗ expression system and an amphipathic polymer and investigation of its in vitro binding preference to G α proteins.

Human lysophosphatidic acid receptor 2 (LPA ₂ ), a member of the G-protein coupled receptor family, mediates lysophosphatidic acid (LPA)-dependent signaling by recruiting various G proteins. Particularly, it is directly implicated in the progression of colorectal and ovarian cancer through G protein signaling cascades. To investigate the biochemical binding properties of LPA ₂ against various alpha subunits of G protein (G _α ), a functional recombinant LPA ₂ was overexpressed in E. coli membrane with a P9 ^∗ expression system, and the purified protein was stabilized with an amphipathic polymer that had been synthesized by coupling octylamine, glucosamine, and diethyl aminoproylamine at the carboxylic groups of poly-γ-glutamic acid. The purified LPA ₂ stabilized with the amphipathic polymer showed selective binding activity to the various G _α proteins as well as agonist-dependent dissociation from G _αi3 . Understanding the binding properties of LPA ₂ against various G _α proteins advances the understanding of downstream signaling cascades of LPA ₂ . The functional LPA ₂ prepared using a P9 ^∗ expression system and an amphipathic polymer could also facilitate the development of LPA ₂ -targeting drugs.
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