UDP-glucose ceramide glucosyltransferase specifically upregulated in plasmacytoid dendritic cells regulates type I interferon production upon CpG stimulation

Plasmacytoid dendritic cells (pDCs) are a distinct subset of DCs involved in immune regulation and antiviral immune responses. Recent studies have elucidated the metabolic profile of pDCs and reported that perturbations in amino acid metabolism can modulate their immune functions. Glycolipid metabolism is suggested to be highly active in pDCs; however, its significance remains unclear. In this study, bulk RNA-sequencing analysis confirmed the known pDC-marker expressions, including interleukin (IL) IL )-3R 3R (CD123), BDCA-2 (CD303), BDCA-4 (CD304), and toll-like receptor 9, compared with that of myeloid DCs (mDCs). Among the differentially expressed genes, UDP-glucose-ceramide glucosyltransferase ( UGCG ) expression was significantly upregulated in pDCs than in mDCs. Moreover, pDC-specific UGCG expression was observed at both the mRNA and protein levels in pDCs and pDC-like cell lines, including CAL-1 and PMDC05 cell lines. Pharmacological or clustered regularly interspaced palindromic repeat (CRISPR)/CRISPR-associated protein 9-mediated genetic inhibition of UGCG did not affect the pDC phenotype as evidenced by the persistent expression of IL-3R and BDCA-2 in pDC-like cell lines. However, UGCG knockout resulted in reduced type I interferon production in pDCs upon CpG activation. In addition, UGCG-knockout pDC-like cell lines exhibited reduced transduction by vesicular stomatitis virus-G pseudo-typed lentiviral vectors, suggesting that low UGCG expression hinders infectivity. Collectively, our findings suggest that pDC-specific UGCG expression is critical for cytokine production and antiviral immune responses in pDCs.