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Identification of a novel region of the GABA B2 C‐terminus that regulates surface expression and neuronal targeting of the GABA B receptor
Author(s) -
Pooler A. M.,
Gray A. G.,
McIlhinney R. A. J.
Publication year - 2009
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2009.06636.x
Subject(s) - endoplasmic reticulum , gabaa receptor , hek 293 cells , receptor , microbiology and biotechnology , endoglycosidase h , chemistry , c terminus , protein subunit , transfection , biochemistry , biology , amino acid , golgi apparatus , gene
GABA B is a G protein‐coupled receptor composed of two subunits, GABA B1 and GABA B2 . GABA B1 contains an endoplasmic reticulum‐retention sequence and is trafficked to the cell surface only in association with GABA B2 . To determine whether the C‐terminus of GABA B2 regulates GABA B trafficking, we constructed forms of GABA B2 with various C‐terminal truncations and examined their surface expression. Truncation of GABA B2 after residue 841 significantly reduced surface expression of both the subunit and the heterodimerized receptor. Turnover of the Δ841 construct, however, did not differ from that of full‐length GABA B2 . To determine whether the C‐terminus of GABA B2 might target GABA B to neurites, cultured hippocampal neurons were transfected with the truncated GABA B2 constructs. Truncation of GABA B2 at residue 841 resulted in primarily somatic localization; furthermore, axonal trafficking of this construct was significantly more restricted than dendritic trafficking. Finally, to biochemically assess trafficking of the truncated GABA B2 constructs, we digested transfected HEK293 cell lysates with endoglycosidase H. When GABA B2 was truncated at residue 841, it became sensitive to digestion by this enzyme, indicating incomplete trafficking. Taken together, these data show that the region of the GABA B2 C‐terminus between residues 841 and 862 is important for regulating forward trafficking and neuronal targeting of the GABA B receptor.