Type 1 polyisoprenoid diphosphate phosphatase modulates geranylgeranyl-mediated control of HMG CoA reductase and UBIAD1.

Rania Elsabrouty,Youngah Jo,Seonghwan Hwang,Russell A Debose-Boyd,Dong-Jae Jun

doi:10.7554/elife.64688

Abstract

UbiA prenyltransferase domain-containing protein-1 (UBIAD1) utilizes geranylgeranyl pyrophosphate (GGpp) to synthesize the vitamin K2 subtype menaquinone-4. The prenyltransferase has emerged as a key regulator of sterol-accelerated, endoplasmic reticulum (ER)-associated degradation (ERAD) of HMG CoA reductase, the rate-limiting enzyme in synthesis of cholesterol and nonsterol isoprenoids including GGpp. Sterols induce binding of UBIAD1 to reductase, inhibiting its ERAD. Geranylgeraniol (GGOH), the alcohol derivative of GGpp, disrupts this binding and thereby stimulates ERAD of reductase and translocation of UBIAD1 to Golgi. We now show that overexpression of Type 1 polyisoprenoid diphosphate phosphatase (PDP1), which dephosphorylates GGpp and other isoprenyl pyrophosphates to corresponding isoprenols, abolishes protein geranylgeranylation as well as GGOH-induced ERAD of reductase and Golgi transport of UBIAD1. Conversely, these reactions are enhanced in the absence of PDP1. Our findings indicate PDP1-mediated hydrolysis of GGpp significantly contributes to a feedback mechanism that maintains optimal intracellular levels of the nonsterol isoprenoid.

Highlights

Mevalonate is a crucial intermediate in a branched pathway that produces cholesterol and nonsterol isoprenoids such as farnesyl pyrophosphate (Fpp), geranylgeranyl pyrophosphate (GGpp), ubiquinone-10, dolichol, heme, and the vitamin K2 subtype menaquinone-4 (MK-4).metabolism play essential roles in a variety of cellular processes ranging from the maintenance of membrane structure, protein prenylation (Fpp and GGpp) and asparagine-linked glycosylation to electron transport and -carboxylation of glutamate residues in specific proteins (MK-4) (Goldstein and Brown, 1990; Wang and Casey, 2016)
We began the exploration into a role for PDP1 in sterol-accelerated ERAD of reductase by generating a line of cells designated SV-589/PDP1-Myc-FLAG that stably express tetracycline-inducible PDP1 tagged at the C
Labeled with azido-GGOH, which is converted into a pyrophosphate derivative that can be utilized for protein geranylgeranylation (Chan et al, 2009; Palsuledesai et al, 2016)

Summary

INTRODUCTION

Mevalonate is a crucial intermediate in a branched pathway that produces cholesterol and nonsterol isoprenoids such as farnesyl pyrophosphate (Fpp), geranylgeranyl pyrophosphate (GGpp), ubiquinone-10, dolichol, heme, and the vitamin K2 subtype menaquinone-4 (MK-4). ERAD of reductase becomes inhibited by the ER sequestered, SCD-associated UBIAD1, which leads to enhanced synthesis and intracellular accumulation of cholesterol in both cultured cells and tissues of knock-in mice that express SCD-associated UBIAD1 (Jo et al, 2019; Schumacher et al, 2018) This new player, UbiA prenyltransferase domain-containing protein-1 (UBIAD1), Missense mutations in the UBIAD1 gene cause Schnyder corneal. Metabolic labeling studies revealed that FOH and GGOH can become converted to their phosphorylated derivatives (Fpp and GGpp) and utilized for the synthesis of sterols and protein prenylation (Crick et al, 1997) Kinases that phosphorylate these isoprenols have been reported in plants and bacteria (Ohnuma et al, 1996; Thai et al, 1999); mammalian counterparts of these enzyme remain to be identified and characterized. We explore a role for PDP1 in the geranylgeranyl-regulated ERAD of

RESULTS

DISCUSSION

MATERIALS AND METHODS