OSBP-related protein-2 (ORP2): a novel Akt effector that controls cellular energy metabolism

• Published in: Cellular and molecular life sciences : CMLS Vol. 75; no. 21; pp. 4041 - 4057
• Main Authors: Kentala, Henriikka, Koponen, Annika, Vihinen, Helena, Pirhonen, Juho, Liebisch, Gerhard, Pataj, Zoltan, Kivelä, Annukka, Li, Shiqian, Karhinen, Leena, Jääskeläinen, Eeva, Andrews, Robert, Meriläinen, Leena, Matysik, Silke, Ikonen, Elina, Zhou, You, Jokitalo, Eija, Olkkonen, Vesa M.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.11.2018; Springer Nature B.V
• Subjects: Acidification; Actin; Actin Cytoskeleton - genetics; Actin Cytoskeleton - metabolism; AKT protein; Biochemistry; Biological Transport - genetics; Biomedical and Life Sciences; Biomedicine; Carbohydrate metabolism; Carbohydrates; Cell adhesion & migration; Cell Biology; Cell culture; Cell Cycle Proteins - genetics; Cell Line; Cell migration; Cell Movement - genetics; Cell Proliferation - genetics; Chaperonins - genetics; Cholesterol; CRISPR; Cytoskeleton; Endoplasmic reticulum; Energy metabolism; Energy Metabolism - genetics; Gene expression; Gene Knockout Techniques; Gene sequencing; Genetic modification; Genome editing; Glycogen; Glycogen synthase kinase 3; Glycolysis; Hepatoma; HSP90 Heat-Shock Proteins; Hsp90 protein; Humans; Kinases; Life Sciences; Lipid metabolism; Lipid Metabolism - genetics; Localization; Metabolism; Organelles - genetics; Organelles - metabolism; Original; Original Article; Proteins; Proto-Oncogene Proteins c-akt - genetics; Proto-Oncogene Proteins c-akt - metabolism; Receptors, Steroid - genetics; Ribonucleic acid; RNA; RNA, Messenger - genetics; Signal Transduction - genetics; Signaling; Steroidogenesis; Sterol regulatory element-binding protein; Synthesis; Transcription; Transmission electron microscopy; Triglycerides; Glycolysis; Akt signaling; OSBP-related protein; Triacylglycerol; CRISPR-Cas9; OSBPL2
• ISSN: 1420-682X; 1420-9071
• DOI: 10.1007/s00018-018-2850-8

ORP2 is a ubiquitously expressed OSBP-related protein previously implicated in endoplasmic reticulum (ER)—lipid droplet (LD) contacts, triacylglycerol (TG) metabolism, cholesterol transport, adrenocortical steroidogenesis, and actin-dependent cell dynamics. Here, we characterize the role of ORP2 in carbohydrate and lipid metabolism by employing ORP2-knockout (KO) hepatoma cells (HuH7) generated by CRISPR-Cas9 gene editing. The ORP2-KO and control HuH7 cells were subjected to RNA sequencing, analyses of Akt signaling, carbohydrate and TG metabolism, the extracellular acidification rate, and the lipidome, as well as to transmission electron microscopy. The loss of ORP2 resulted in a marked reduction of active phosphorylated Akt(Ser473) and its target Glycogen synthase kinase 3β(Ser9), consistent with defective Akt signaling. ORP2 was found to form a physical complex with the key controllers of Akt activity, Cdc37, and Hsp90, and to co-localize with Cdc37 and active Akt(Ser473) at lamellipodial plasma membrane regions, in addition to the previously reported ER–LD localization. ORP2-KO reduced glucose uptake, glycogen synthesis, glycolysis, mRNA-encoding glycolytic enzymes, and SREBP-1 target gene expression, and led to defective TG synthesis and storage. ORP2-KO did not reduce but rather increased ER–LD contacts under basal culture conditions and interfered with their expansion upon fatty acid loading. Together with our recently published work (Kentala et al. in FASEB J 32:1281–1295, 2018 ), this study identifies ORP2 as a new regulatory nexus of Akt signaling, cellular energy metabolism, actin cytoskeletal function, cell migration, and proliferation.