Lipid and Metabolism

Perilipin 2 belongs to the Perilipin family, which consists of proteins that coat intracellular lipid storage droplets. Perilipin 2 in particular is involved in lipid globule surface membrane composition, and has also been implicated in the development and maintenance of adipose tissue. Contrary to previous findings, Perilipin 2 is found in a variety of cells aside from adipocytes, ranging from fibroblasts to skin cells.

The human form of microtubule-associated protein light chain 3 (LC3) is expressed as 3 splice variants LC3A, LC3B, and LC3C.¹ LC3B is a subunit of the MAP1A and MAP1B microtubule-binding proteins and plays a central role in autophagosome membrane structure.

The bile acid-responsive G-protein-coupled receptor TGR5 is widely distributed across the human body - including the endocrine glands, adipocyte cells, muscles, immune organs, spinal cord, and the enteric nervous system. G protein coupled receptors (GPCRs) are incredibly versatile signaling molecules that are activated by a number of ligands, which in turn regulate various signaling pathways.

ChREBP (carbohydrate response element-binding protein) is a glucose responsive basic helix-loop-helix/leucine zipper (bHLH/LZ) transcription factor that binds MLX and then carbohydrate response element /ChoRE for the induction of genes involved in glycolysis, de novo lipogenesis (DNL), and fatty acid desaturation. ChREBP’s target genes includes glucokinase (GCK), fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), pyruvate kinase/liver type pyruvate kinase (PK1/ PKLR), delta-9-desaturase (SCD/SCD1) etc.

Succinate dehydrogenase (SDH) is a highly conserved protein complex located on the inner mitochondrial membrane where it functions during the Krebs cycle by oxidizing succinate to fumarate (1). This reaction is also important for feeding electrons into the electron transport chain. SDH complex contains four subunits: SDH-A, -B, -C, and -D. Mutation of SDH-A often leads to mitochondrial encephalopathy while mutations to subunits B, C, and D lead to tumors of the head and neck (1).

SUCNR1 is the cognate receptor for the Kreb's citric acid cycle intermediate succinate. It is of interest to scientists because it is involved in not only energy metabolism but possibly also in renovascular hypertension, a condition linked to diabetes, renal failure, and atherosclerosis.  This G-protein coupled receptor is most highly expressed in the kidney - predominantly in the proximal tubules. Two signaling pathways have been identified downstream from SUCNR1: a pertussis-toxin-sensitive Gi/Go pathway, as well as a pertussis-toxin-insensitive Gq pathway.

MCT1 is a proton-linked transport carrier that catalyzes the movement of short chain monocarboxylates (branched-chain oxo acids derived from leucine, valine, and isoleucine) across both plasma and inner mitochondrial membranes. In particular, substances such as lactate, pyruvate, butyrate, and ketone bodies are shuttled; these play big roles in cell metabolism particularly in tissues and organs like the kidney, intestine, liver, and brain.

The ATP-binding cassette transporter A1 (ABCA1) protein is a key gatekeeper for regulating intracellular cholesterol transport. It is one member of a large family of genes comprised of cAMP-dependent anion transporter cell membrane proteins. These important proteins regulate reverse cholesterol efflux from cells into the peripheral tissues via apolipoprotein A-1 (apo). ABCA1 in particular has a diverse expression profile and is most highly expressed in macrophages.

Protein arginine methylation is a prevalent posttranslational modification in eukaryotic cells. It regulates RNA processing, trafficking and nascent pre-RNA metabolism, receptor-mediated signal transduction, and transcriptional activation processes. PRMT6 was originally identified through a genome-wide search for human protein arginine N-methyltransferase (PRMT) family members. This particular enzyme has type I PRMT activity and with regards to substrate specificity, is functionally distinct from two other previously characterized type I enzymes - PRMT1 and PRMT4.