SCP2

This gene encodes two proteins: sterol carrier protein X (SCPx) and sterol carrier protein 2 (SCP2), as a result of transcription initiation from 2 independently regulated promoters. The transcript initiated from the proximal promoter encodes the longer SCPx protein, and the transcript initiated from the distal promoter encodes the shorter SCP2 protein, with the 2 proteins sharing a common C-terminus. Evidence suggests that the SCPx protein is a peroxisome-associated thiolase that is involved in the oxidation of branched chain fatty acids, while the SCP2 protein is thought to be an intracellular lipid transfer protein. This gene is highly expressed in organs involved in lipid metabolism, and may play a role in Zellweger syndrome, in which cells are deficient in peroxisomes and have impaired bile acid synthesis. Alternative splicing of this gene produces multiple transcript variants, some encoding different isoforms. The full-length nature of all transcript variants has not been determined. [provided by RefSeq]

Full Name

sterol carrier protein 2

Function

Isoform SCPx
Plays a crucial role in the peroxisomal oxidation of branched-chain fatty acids (PubMed:10706581).
Catalyzes the last step of the peroxisomal beta-oxidation of branched chain fatty acids and the side chain of the bile acid intermediates di- and trihydroxycoprostanic acids (DHCA and THCA) (PubMed:10706581).
Also active with medium and long straight chain 3-oxoacyl-CoAs. Stimulates the microsomal conversion of 7-dehydrocholesterol to cholesterol and transfers phosphatidylcholine and 7-dehydrocholesterol between membrances, in vitro (By similarity).
Isoforms SCP2 and SCPx cooperate in peroxisomal oxidation of certain naturally occurring tetramethyl-branched fatty acyl-CoAs (By similarity).
Isoform SCP2
Mediates the transfer of all common phospholipids, cholesterol and gangliosides from the endoplasmic reticulum to the plasma membrane. May play a role in regulating steroidogenesis (PubMed:17157249, PubMed:8300590, PubMed:7642518).
Stimulates the microsomal conversion of 7-dehydrocholesterol to cholesterol (By similarity).
Also binds fatty acids and fatty acyl Coenzyme A (CoA) such as phytanoyl-CoA. Involved in the regulation phospholipid synthesis in endoplasmic reticulum enhancing the incorporation of exogenous fatty acid into glycerides. Seems to stimulate the rate-limiting step in phosphatidic acid formation mediated by GPAT3. Isoforms SCP2 and SCPx cooperate in peroxisomal oxidation of certain naturally occurring tetramethyl-branched fatty acyl-CoAs (By similarity).

Biological Process

Biological Process alpha-linolenic acid metabolic processTAS:Reactome
Biological Process bile acid biosynthetic processTAS:Reactome
Biological Process bile acid metabolic processISS:UniProtKB
Biological Process fatty acid beta-oxidationISS:UniProtKB
Biological Process fatty acid beta-oxidation using acyl-CoA oxidaseTAS:Reactome
Biological Process inositol trisphosphate biosynthetic processIDA:UniProtKB
Biological Process intracellular cholesterol transportIMP:UniProtKB
Biological Process lipid hydroperoxide transportManual Assertion Based On ExperimentIDA:UniProtKB
Biological Process phospholipid transportManual Assertion Based On ExperimentIDA:UniProtKB
Biological Process positive regulation of intracellular cholesterol transportManual Assertion Based On ExperimentIDA:UniProtKB
Biological Process positive regulation of steroid metabolic processIDA:UniProtKB
Biological Process progesterone biosynthetic processIDA:UniProtKB
Biological Process protein localization to plasma membraneIDA:UniProtKB
Biological Process regulation of phospholipid biosynthetic processISS:UniProtKB
Biological Process steroid biosynthetic processManual Assertion Based On ExperimentIDA:UniProtKB

Cellular Location

Isoform SCP2
Peroxisome
Cytoplasm
Mitochondrion
Endoplasmic reticulum
Mitochondrion
Isoform SCPx
Peroxisome

Involvement in disease

Leukoencephalopathy with dystonia and motor neuropathy (LKDMN):
A syndrome characterized by leukoencephalopathy, dystonic head tremor, spasmodic torticollis and reduced tendon reflexes in lower extremities. Additional features include hyposmia, pathologic saccadic eye movements, a slight hypoacusis, accumulation of branched-chain pristanic acid in plasma, and the presence of abnormal bile alcohol glucuronides in urine.

PTM

Isoform SCP2
preSCP2, a protein with a molecular mass of about 15 kDa, is processed into its mature form (SCP2) by proteolytic cleavage of a 20 residue leader sequence after translocation into peroxisomes.