TY - JOUR
T1 - Regulation of glucosylceramide synthesis by Golgi-localized phosphoinositide
AU - Ishibashi, Yohei
AU - Ito, Makoto
AU - Hirabayashi, Yoshio
N1 - Funding Information:
We are grateful to the Support Unit for Bio-material Analysis, RIKEN Brain Science Institute Research Resources Center, for help with the nucleotide sequencing analyses. This work was supported in part by the RIKEN Special Postdoctoral Researchers Program (to Y. I.), and a Grant-in-Aid for Young Scientists (B) (to Y. I.) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan ( 24770198 ).
Publisher Copyright:
© 2018 Elsevier Inc.
PY - 2018/5/23
Y1 - 2018/5/23
N2 - 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)P2. 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.
AB - 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)P2. 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.
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U2 - 10.1016/j.bbrc.2018.04.039
DO - 10.1016/j.bbrc.2018.04.039
M3 - Article
C2 - 29627573
AN - SCOPUS:85045409648
VL - 499
SP - 1011
EP - 1018
JO - Biochemical and Biophysical Research Communications
JF - Biochemical and Biophysical Research Communications
SN - 0006-291X
IS - 4
ER -