Abstract
Peroxisomes are single-membrane organelles present in eukaryotes. The functional importance of peroxisomes in humans is represented by peroxisome-deficient peroxisome biogenesis disorders (PBDs), including Zellweger syndrome. Defects in the genes that encode the 14 peroxins that are required for peroxisomal membrane assembly, matrix protein import and division have been identified in PBDs. A number of recent findings have advanced our understanding of the biology, physiology and consequences of functional defects in peroxisomes. In this Review, we discuss a cooperative cell defense mechanisms against oxidative stress that involves the localization of BAK (also known as BAK1) to peroxisomes, which alters peroxisomal membrane permeability, resulting in the export of catalase, a peroxisomal enzyme. Another important recent finding is the discovery of a nucleoside diphosphate kinase-like protein that has been shown to be essential for how the energy GTP is generated and provided for the fission of peroxisomes. With regard to PBDs, we newly identified a mild mutation, Pex26-F51L that causes only hearing loss. We will also discuss findings from a new PBD model mouse defective in Pex14, which manifested dysregulation of the BDNF-TrkB pathway, an essential signaling pathway in cerebellar morphogenesis. Here, we thus aim to provide a current view of peroxisome biogenesis and the molecular pathogenesis of PBDs.
Highlights
The peroxisome is a ubiquitous, single-membrane-bounded intracellular organelle present in almost all, if not all, eukaryotes
The importance of peroxisomal function is highlighted by fatal human genetic peroxisomal biogenesis disorders (PBDs), including Zellweger spectrum disorders (ZSDs), which account for ∼80% of the patients with PBDs, including Heimler syndrome (Ratbi et al, 2015) and rhizomelic chondrodysplasia punctate (RCDP) (Weller et al, 2003)
Peroxins are classified into three groups: (1) Pex3, Pex16 and Pex19, which are essential for peroxisome membrane assembly via classes I and II pathways; (2) ten peroxins that are required for matrix protein import; and (3) the different isoforms of Pex11, namely Pex11α, Pex11β and Pex11γ, which are involved in peroxisome division together with dynamin-like protein 1 (DLP1, known as DNM1L), mitochondrial fission factor (Mff ) and mitochondrial fission protein 1 (Fis1) (Fujiki, 2016; Platta et al, 2016; Farré et al, 2019) (Fig. 1)
Summary
The peroxisome is a ubiquitous, single-membrane-bounded intracellular organelle present in almost all, if not all, eukaryotes.
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