PIP4K2A regulates intracellular cholesterol transport through modulating PI(4,5)P2 homeostasis

Abstract

The transport of LDL-derived cholesterol from lysosomes to peroxisomes is mediated by membrane contacts, which are facilitated by the lysosomal protein synaptotagmin VII and the peroxisomal lipid phosphatidylinositol 4, 5-bisphosphate (PI(4,5)P 2 ). Here, we used RNA interference to search for regulators of PI(4,5)P 2 and to study the effects of altered PI(4,5)P 2 homeostasis on cholesterol transport. We found that knockdown of phosphatidylinositol 5-phosphate 4-kinase type-2 alpha (PIP4K2A) reduced peroxisomal PI(4,5)P 2 levels, decreased lysosome-peroxisome membrane contacts, and increased accumulation of lysosomal cholesterol in human SV-589 fibroblasts. Forced expression of peroxisome-localized, kinase-active PIP4K2A in the knockdown cells reduced cholesterol accumulation, and in vitro addition of recombinant PIP4K2A restored membrane contacts.These results suggest that PIP4K2A plays a critical role in intracellular cholesterol transport by up-regulating PI(4,5)P 2 in the peroxisome membrane. Further research into PIP4K2A activity may inform future therapeutic interventions for managing lysosomal storage disorders.

Defining the Subcellular Distribution and Metabolic Channeling of Phosphatidylinositol

“…Briefly, fractionation studies show that PtdIns represents ∼5% of the total phospholipid content of the peroxisomes (Hardeman et al, 1990) as well as suggest, relative to other inositol-containing lipids, that the levels of PtdIns4P, PtdIns(3,5)P 2 , and PtdIns(4,5)P 2 are enriched in peroxisomal membranes (Jeynov et al, 2006). The potential for a specific enrichment of PPIn lipids is supported by recent reports describing the interaction of PtdIns(4,5)P 2 present on the peroxisome surface with the lysosomal protein synaptotagmin VII to establish contact sites between lysosomes and peroxisomes (Chu et al, 2015; Hu et al, 2018). More studies will be needed to define the role of PtdIns and PPIn species in these compartments.…”

Defining the subcellular distribution and metabolic channeling of phosphatidylinositol

“…(Hardeman et al, 1990), and more recent measurements suggest that, among PPIn species, the levels of PI4P, PI(3,5)P 2 , and PI(4,5)P 2 are enriched in peroxisomal membranes (Jeynov et al, 2006). The potential for a specific role for PPIn lipids in peroxisomes is supported by recent reports describing interaction between PI(4,5)P 2 present on the peroxisome surface and the lysosomal protein synaptotagmin VII, which is important for establishing functionally relevant contact sites between lysosomes and peroxisomes (Chu et al, 2015;Hu et al, 2018). Undoubtedly, additional studies are needed to better define the role of PI and PPIn species within these diverse compartments.…”

X‐linked adrenoleukodystrophy: Pathology, pathophysiology, diagnostic testing, newborn screening and therapies

“…In 2015, the Bao-Liang Song research group demonstrated that cholesterol transport is abnormal in ALD fibroblasts and in the Abcd1 mouse model for ALD as well as in other peroxisomal disorders. Low-density lipoprotein (LDL)-derived cholesterol was transported from the lysosome to the peroxisome in a manner that depended upon lysosomal synaptotagmin VII binding to the peroxisomal lipid phosphatidylinositol 4, 5-bisphosphate [PI(4,5)P 2 ] on the peroxisomal membrane (Chu et al, 2015;Hu et al, 2018;Islinger, Voelkl, Fahimi, & Schrader, 2018;Jin, Strunk, & Weisman, 2015;Luo, Jiang, Yang, & Song, 2018;Luo, Liao, Xiao, & Song, 2017;Stefan et al, 2017). While these findings were initially called into question by van Veldhoven et al in a letter to the editor (van Veldhoven, Baes, & Fransen, 2015), correctly identifying an error in Chu et al's method, a recent follow-up publication (Xiao et al, 2019) validates the initial Chu et al (2015) findings.…”