THE ALDEHYDE DEHYDROGENASE ALDH2-ASTERISK-2 ALLELE EXHIBITS DOMINANCEOVER ALDH2-ASTERISK-1 IN TRANSDUCED HELA-CELLS

Individuals heterozygous or homozygous for the variant aldehyde dehydr ogenase (ALDH2) allele (ALDH22), which encodes a protein differing on ly at residue 487 from the normal protein, have decreased ALDH2 activi ty in liver extracts and experience cutaneous flushing when they drink alcohol, The mechanism by which this allele exerts its dominant effec t is unknown, To study this effect, the human ALDH21 cDNA was cloned and the ALDH22 allele was generated by site-directed mutagenesis. The se cDNAs were transduced using retroviral vectors into HeLa and CV1 ce lls, which do not express ALDH2, The normal allele directed synthesis of immunoreactive ALDH2 protein (ALDH2E) with the expected isoelectric point, Extracts of these cells contained increased aldehyde dehydroge nase activity with low K-m for the aldehyde substrate, The ALDR22 all ele directed synthesis of mRNA and immunoreactive protein (ALDH2K), bu t the protein lacked enzymatic activity, When ALDH21-expressing cells were transduced with ALDH22 vectors, both mRNAs were expressed and i mmunoreactive proteins with isoelectric points ranging between those o f ALDH2E and ALDH2K were present, indicating that the subunits formed heteromers, ALDH2 activity in these cells was reduced below that of th e parental ALDH21-expressing cells, Thus, the ALDH2*2 allele is suffi cient to cause ALDH2 deficiency in vitro.