GENERATION OF A MAMMALIAN-CELL LINE DEFICIENT IN GLUCOSEREGULATED PROTEIN STRESS INDUCTION THROUGH TARGETED RIBOZYME DRIVEN BY A STRESS-INDUCIBLE PROMOTER

GRP94 is an endoplasmic reticulum (ER) localized glycoprotein with Ca2 + binding and protein chaperoning properties. Using a ribozyme driven by a stress-inducible promoter and targeted against grp94 mRNA, we hav e generated a cell line deficient in its ability to induce GRP94. The effect of the ribozyme is mediated by the cleavage of the grp94 messag e just downstream of the initiation codon, and not by an antisense eff ect, as determined by the level of intact grp94 mRNA. Unexpectedly, th is cell line's ability to induce GRP78 is also impaired. Transient ove rexpression of recombinant human lysosomal hydrolase alpha-L-iduronida se in the ribozyme expressing cells indicates that the secretion ratio of this enzyme is reduced by about B-fold. Additionally, the ribozyme expressing cells showed increased sensitivity to Ca2+ depletion from ER caused by either A23187 or thapsigargin, an ER-Ca2+-ATPase inhibito r, but not to tunicamycin. These combined results show that the induct ion of GRP94 may play important roles in ER to nuclear signaling, prot ein sorting and secretion, and specific protection against Ca2+ deplet ion stress.