ETHANOL-RESPONSIVE GENES IN NEURAL CELLS INCLUDE THE 78-KILODALTON GLUCOSE-REGULATED PROTEIN (GRP78) AND 94-KILODALTON GLUCOSE-REGULATED PROTEIN (GRP94) MOLECULAR CHAPERONES

Previously we found that ethanol increases expression of the constitut ive 70-kDa heat shock protein (Hsc70) in NG108-15 neuroblastoma x glio ma cells. We suggested that known ethanol actions on cellular protein trafficking may relate to Hsc70 induction because Hsc70 functions as a molecular chaperone. Here we use a subtractive hybridization protocol to isolate ethanol-responsive genes (EtRGs). Northern blot hybridizat ion verified ethanol-induced increases in mRNA abundance for five cDNA clones isolated from ethanol-treated NG108-15 neuroblastoma x glioma cells. DNA sequence analysis identified one EtRG as 94-kDa glucose-reg ulated protein (GRP94), a member of the ''glucose-responsive'' subgrou p of stress proteins. Other identified EtRGs included an insulin-induc ed growth-response protein gene and an intracisternal A-type particle gene. Sequence analysis of the remaining two EtRGs showed no homology in DNA sequence databases. All EtRGs showed wide tissue expression, ex cept SL64, which was not detected in Northern blot analyses of adult m ouse or rat tissues. Ethanol also increased mRNA abundance for 78-kDa glucose-regulated protein (GRP78), a molecular chaperone known to func tion in glycoprotein trafficking and usually coordinately regulated wi th GRP94. However, ethanol induced GRP94 more than GRP78, a pattern di stinct from those of other inducers of these genes. All EtRGs, includi ng GRP94 and GRP78, showed similar ethanol concentration-dependent inc reases in mRNA abundance. In contrast, thapsigargin and other inducers of glucose-responsive proteins increased GRP94 and GRP78 mRNA levels without altering expression of other EtRGs. Our studies demonstrate th at several molecular chaperones constitute a subset of EtRGs. Ethanol appears to regulate these EtRGs by a unique mechanism, rather than one shared by classical inducers of stress proteins.