Regulation of glucosylceramide synthesis by Golgi-localized phosphoinositide

Journal Article · Tue May 15 04:00:00 EDT 2018 · Biochemical and Biophysical Research Communications

DOI:https://doi.org/10.1016/J.BBRC.2018.04.039· OSTI ID:23137135

Ishibashi, Yohei; Ito, Makoto ^[1]; Hirabayashi, Yoshio ^[2]

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1. Department of Bioscience and Biotechnology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka, 812-8581 (Japan)
2. Laboratory for Molecular Membrane Neuroscience, RIKEN Brain Science Institute, Wako-shi, Saitama, 351-0198 (Japan)

Highlights: • Phosphoinositide inhibits Glucosylceramide synthase but not Sphingomyelin synthase. • Phosphoinositide inhibits Glucosylceramide synthase by competing with UDP-glucose. • Expression of PH domain increases cellular glucosylceramide synthase activity. • Glucosylceramide synthase and phophatidylinositol-4-phosphate partly colocalize in Golgi. Phosphoinositides mediate a large number of signaling processes in mammalian cells. Here, we report that phophatidylinositol-4-phosphate (PtdIns(4)P) downregulates the cellular glucosylceramide (GlcCer) level by inhibiting the interaction between GlcCer synthase (UGCG) and UDP-glucose in the Golgi apparatus. In this study, we used two PH domain probes to bind phosphoinositides; one derived from FAPP1 for targeting to the Golgi PtdIns(4)P and the other from PLC δ for targeting to the plasma membrane PtdIns(4,5)P{sub 2}. The levels of GlcCer and lactosylceramide, but not of sphingomyelin (SM), were increased following expression of the FAPP1 PH domain in cells, accompanied by an increase in UGCG activity. However, no elevated GlcCer level was observed after expression of the PLC δ PH domain. PtdIns(4)P inhibited UGCG activity, but not SMS activity, in a concentration-dependent manner, and UGCG activity was restored by the addition of UDP-glucose in the reaction mixture. These results indicate that PtdIns(4)P inhibits UGCG activity by competing with UDP-glucose. We conclude that the increase in UGCG activity due to the expression of the FAPP1 PH domain was caused by an attenuation of the inhibitory effect of PtdIns(4)P on UGCG. This study provides new insights into the regulation of GlcCer synthesis by PtdIns(4)P in the Golgi apparatus.

• OSTI ID: 23137135
• Journal Information: Biochemical and Biophysical Research Communications, Journal Name: Biochemical and Biophysical Research Communications Journal Issue: 4 Vol. 499; ISSN 0006-291X; ISSN BBRCA9
• Country of Publication: United States
• Language: English

Related Subjects

60 APPLIED LIFE SCIENCES
GLUCOSE
GOLGI COMPLEXES
NUCLEOTIDES
PHOSPHATES
SACCHAROSE
SPHINGOMYELINS
SYNTHESIS