Effect of gestational ethanol exposure on the NMDA receptor complex in ratforebrain: from gene transcription to cell surface

Effects of gestational ethanol exposure on the trafficking of the NMDA rece ptor complex were investigated. Studies focused on three distinct processes in NMDA receptor translocation: (1) the level of gene transcription (2) na scent NMDA receptor subunits (NR) associated with the endoplasmic reticulum bound chaperone protein calnexin and (3) NMDA receptors associated with th e cell surface anchoring protein PSD-95, Forebrain mRNA and membrane protei ns were isolated from postnatal day I rat pups from prenatally ethanol expo sed, pair-fed and ad libitum experimental groups. Ribonuclease protection a ssays were carried out to determine the levels of NR2A, NR2B, and NR2C mRNA within the treatment groups determined. Results indicated that gestational ethanol exposure did not affect the gene transcription of the NR2 subunits . Immunoprecipitation experiments were conducted with an anti-calnexin anti body or an anti-PSD-95 antibody and the immunoprecipitates probed for NR1 a nd NR2 subunits. Within the anti-calnexin immunoprecipitates, no NR2A, NR2B or NR2C subunits were detectable, but a significant pool of NR1 subunits w as identified. These findings suggest that NR1 subunits but not NR2 subunit s are associated with calnexin within the endoplasmic reticulum. Further, g estational ethanol exposure significantly increased the NR1 polypeptide lev els in the anti-calnexin immunoprecipitate. Anti-PSD-95 immunoprecipitates revealed an abundance of NR1 and NR2B subunits, and these complexes were un affected by gestational ethanol exposure. No NR2A or NR2C subunits were det ected. These results suggest that gestational ethanol exposure significantl y affects the assembly and transport of NMDA receptors. Gestational ethanol exposure may not alter the composition of the PSD-95 associated NMDA recep tor complex. (C) 2001 Elsevier Science BY All rights reserved.