Peroxisome biogenesis in mammalian cells

Abstract

To investigate peroxisome assembly and human peroxisome biogenesis disorders (PBDs) such as Zellweger syndrome, thirteen different complementation groups (CGs) of Chinese hamster ovary (CHO) cell mutants defective in peroxisome biogenesis have been isolated and established as a model research system. Successful gene-cloning studies by a forward genetic approach utilized a rapid functional complementation assay of CHO cell mutants led to isolation of human peroxin (PEX) genes. Search for pathogenic genes responsible for PBDs of all 14 CGs is now completed together with the homology search by screening the human expressed sequence tag database using yeast PEX genes. Peroxins are divided into three groups: (1) peroxins including Pex3p, Pex16p, and Pex19p, are responsible for peroxisome membrane biogenesis via classes I and II pathways; (2) peroxins that function in matrix protein import; (3) those such as three forms of Pex11p, Pex11pα, Pex11pβ, and Pex11pγ, are involved in peroxisome proliferation where DLP1, Mff, and Fis1 coordinately function. In membrane assembly, Pex19p forms complexes in the cytosol with newly synthesized PMPs including Pex16p and transports them to the receptor Pex3p, whereby peroxisomal membrane is formed (Class I pathway). Pex19p likewise forms a complex with newly made Pex3p and translocates it to the Pex3p receptor, Pex16p (Class II pathway). In matrix protein import, newly synthesized proteins harboring peroxisome targeting signal type 1 or 2 are recognized by Pex5p or Pex7p in the cytoplasm and are imported to peroxisomes via translocation machinery. In regard to peroxisome-cytoplasmic shuttling of Pex5p, Pex5p initially targets to an 800-kDa docking complex consisting of Pex14p and Pex13p and then translocates to a 500-kDa RING translocation complex. At the terminal step, Pex1p and Pex6p of the AAA family mediate the export of Pex5p, where Cys-ubiquitination of Pex5p is essential for the Pex5p exit.

Interaction of Phospholipase A/Acyltransferase-3 with Pex19p

“…Metabolic Labeling-Cells were grown at 37°C to 80% confluence in a 6-well plate containing Dulbecco's modified Eagle's medium with 10% fetal calf serum and were labeled with [1][2][3][4][5][6][7][8][9][10][11][12][13][14] C]hexadecanol (1.6 Ci) for 18 h. Cells were then harvested and washed twice with PBS. The total lipids were extracted by the method of Bligh and Dyer (29), spotted on a silica gel thin layer plate (20-cm height), and developed at 4°C for 1 h in hexane/diethyl ether/acetic acid (75:25:1, v/v/v).…”

“…Pex3p, Pex16p, and Pex19p have been identified as peroxins indispensable for peroxisome membrane assembly and PMP transport, and the cells deficient in these proteins are devoid of peroxisome structure itself (8,9). Pex19p is predominantly localized to cytoplasm and binds to various PMPs, whereas Pex3p and Pex16p are associated with peroxisomal membrane and function as the membrane-anchoring site for Pex19p⅐PMP complexes and as the receptor for Pex3p⅐Pex19p complex, respectively (10).…”

Peroxisomal protein PEX 13 functions in selective autophagy

“…During peroxisome biogenesis, PEX13 interacts with PEX14 and PEX5 for peroxisomal matrix protein import, whereas PEX3 and PEX19 function upstream in the formation of peroxisomal membrane 2. Since the peroxisome biogenesis function of PEX13 depends on other peroxin family members, we evaluated whether other peroxins are required for mitophagy and general autophagy.…”

BAK regulates catalase release from peroxisomes

“…1,2 To date, all 14 genes responsible for PBDs, called peroxin genes or PEX, have been identified. [1][2][3] Under intolerable cellular stress such as oxidative stress, the cells are committed to apoptosis through compromising the integrity of the mitochondrial outer membrane by inducing mitochondrial outer membrane permeabilization (MOMP). [4][5][6] MOMP leads to the release of intermembrane-space proteins including cytochrome c, followed by the activation of caspases responsible for the progression of apoptosis.…”