Regulation of UDP-N-acetylglucosamine:dolichyl-phosphate N-acetylglucosamine-1-phosphate transferase by retinoic acid in P19 cells

Abstract

UDP-N-acetylglucosamine:dolichyl-phosphate N-acetylglucosamine-1-phosphate transferase (GPT) is the first enzyme in the dolichol pathway of protein N-glycosylation, and is implicated in the developmental programmes of a variety of eukaryotes. In the present study we describe the effects of all-trans-retinoic acid (RA) on the levels of GPT protein and enzymic activity, and on the transcription rate of the GPT gene, in mouse P19 teratocarcinoma cells. RA caused a dose-dependent and protein-synthesis-dependent induction of enzyme activity. The maximum induction of GPT activity (about 3-fold) required 2 days of exposure to 1 microM RA. Induced GPT activity also resulted in an increase in the rate of incorporation of [3H]mannose into Glc3Man9GlcNAc2. Enzymic activities paralleled GPT gene expression. The GPT gene was induced (2-fold) after 7 h of RA treatment. An approx. 3-fold increase in a 48 kDa GPT protein and approx. 4-fold increases in the levels of three GPT transcripts (1.8, 2.0 and 2.2 kb) were observed after 2 days of RA treatment. The enhanced levels of GPT protein and mRNAs began to decline 3 days after the initiation of differentiation, and GPT expression was down-regulated during cellular differentiation. GPT activity decreased about 2. 8-fold to a constant level in differentiated P19 cells. The results indicate that the RA-induced enzyme activity was mainly determined by increased transcription of the GPT gene. RA-treated P19 cells were about 4-fold more resistant to tunicamycin, a fungal antibiotic which inhibits GPT, than were control cells. In addition, GPT activity in membranes from RA-treated P19 cells exhibited approx. 4-fold increased resistance to tunicamycin compared with activity in membranes from untreated control cells, demonstrating that resistance to tunicamycin is correlated with induced GPT activity. Furthermore, increased GPT activity had regulatory significance with regard to the rate of incorporation of [3H]mannose into Glc3Man9GlcNAc2-P-P-dolichol and into glycoproteins. Together, the data provide additional insights into the hormonal regulation of GPT and present evidence that the RA-mediated induction of GPT has a regulatory impact on the dolichol pathway.

Microarray analysis of retinoid‐dependent gene activity during rat embryogenesis: Increased collagen fibril production in a model of retinoid insufficiency

“…The net consequence of these increased gene expressions could increase the galactose pools available for protein and lipid glycosylation. Such changes could have functional consequences to the embryo, because glycoproteins and glycolipids are important modulators of cellular adhesion, migration, and differentiation; for example, several glycosyltransferases are rapidly up‐regulated in RA‐treated embryonal carcinoma cell lines (Yang et al, 1994; Cho et al, 1996; Meissner et al, 1999). Elevation of galactosylation‐related transcripts in RAD embryos is also consistent with the enhanced galactose phosphate and UDP‐galactose synthesis seen in vitamin A‐deficient rats (Shankar et al, 1990).…”

N-Glycosylation and Residue 96 Are Involved in the Functional Properties of UDP-Glucuronosyltransferase Enzymes,

“…Thus, it was suggested this may be due to mutation of a transcription factor required for the regulation of both genes. Moreover, expression of UGT, GlcNAc, and UDP-N-acetylglucosamine: dolichylphosphate N-acetylglucosamine-1-phosphate transferase (GPT), an enzyme which is involved in the dodichol pathway of protein N-glycosylation, is upregulated by retinoic acid (13,14).…”