Sterol transfer, PI 4P consumption, and control of membrane lipid order by endogenous OSBP

Abstract

The network of proteins that orchestrate the distribution of cholesterol among cellular organelles is not fully characterized. We previously proposed that oxysterol-binding protein (OSBP) drives cholesterol/PI4P exchange at contact sites between the endoplasmic reticulum (ER) and the -Golgi network (TGN). Using the inhibitor OSW-1, we report here that the sole activity of endogenous OSBP makes a major contribution to cholesterol distribution, lipid order, and PI4P turnover in living cells. Blocking OSBP causes accumulation of sterols at ER/lipid droplets at the expense of TGN, thereby reducing the gradient of lipid order along the secretory pathway. OSBP consumes about half of the total cellular pool of PI4P, a consumption that depends on the amount of cholesterol to be transported. Inhibiting the spatially restricted PI4-kinase PI4KIIIβ triggers large periodic traveling waves of PI4P across the TGN These waves are cadenced by long-range PI4P production by PI4KIIα and PI4P consumption by OSBP Collectively, these data indicate a massive spatiotemporal coupling between cholesterol transport and PI4P turnover via OSBP and PI4-kinases to control the lipid composition of subcellular membranes.

Phosphatidylinositol 4,5‐bisphosphate controls Rab7 and PLEKHM 1 membrane cycling during autophagosome–lysosome fusion

“…It has been reported that inactivation of the ER‐localized adaptor proteins VAP‐A and VAP‐B leads to the accumulation of PI4P in endosomes due to the inability of the OSBP protein to transport PI4P from endosomes to the ER (Dong et al , ). Indeed, inhibition of OSBP by OSW1 was reported to induce accumulation of Golgi and endosomal PI4P (Mesmin et al , ). Therefore, we set out experiments to investigate the effect of OSW1 on endosomal PI4P.…”

“…PI4P and PI4K2A were also found to organize important multi‐component signaling complexes on endosomes such as the lysosome‐related organelles complex 1 (BLOC‐1) and the Wiskott‐Aldrich Syndrome Protein and SCAR Homolog (WASH) complexes (Newell‐Litwa et al , ; Ryder et al , ; Dong et al , ). Lastly, PI4P levels on endosomes are also regulated by lipid‐transfer proteins of the OSBP family, suggesting that endosomal PI4P is utilized to drive the transport of lipids between the ER and endosomes (Dong et al , ; Mesmin et al , ).…”

Characterization of the c10orf76‐PI4KB complex and its necessity for Golgi PI4P levels and enterovirus replication

“…Phosphorylation of PI4KB by PKD at Ser294 mediates binding to 14-3-3 proteins, with this leading to an increase in PI4KB activity [22,23], that has been suggested to correspond with an increase in PI4KB stability [24]. In addition to regulatory protein interactions, PI4KB is predicted to contain an amphipathic lipid packing sensor (ALPS) motif at the C-terminus that mediates lipid binding to unsaturated membranes [9]. ACBD3 forms a direct, high-affinity interface with PI4KB that is mediated by a disorder-to-order transition in the N-terminus of PI4KB upon binding to the Q domain of ACBD3 [11,12].…”

“…Multiple human pathogens manipulate PI4P levels to mediate their intracellular replication, including Legionella [3] and multiple picornaviruses [4,5]. PI4KB is localized at the Golgi and trans-Golgi network (TGN), with PI4P pools in the Golgi apparatus generated by both PI4K2A and PI4KB [9]. PI4KB is localized at the Golgi and trans-Golgi network (TGN), with PI4P pools in the Golgi apparatus generated by both PI4K2A and PI4KB [9].…”

Direct trafficking pathways from the Golgi apparatus to the plasma membrane

“…FAPP2 transfers GlcCer to the trans-Golgi [112] as described in section 5.1 above. At membrane contact sites, OSBP directs cholesterol transfer from the ER to the trans-Golgi through coupled counter-transport of PI(4)P [142,186]. CERT transports ceramide from the ER to the trans-Golgi [187], thereby promoting SM and diacylglycerol synthesis.…”