Pex11mediates peroxisomal proliferation by promoting deformation of the lipid membrane

Abstract

Pex11p family proteins are key players in peroxisomal fission, but their molecular mechanisms remains mostly unknown. In the present study, overexpression of Pex11pβ caused substantial vesiculation of peroxisomes in mammalian cells. This vesicle formation was dependent on dynamin-like protein 1 (DLP1) and mitochondrial fission factor (Mff), as knockdown of these proteins diminished peroxisomal fission after Pex11pβ overexpression. The fission-deficient peroxisomes exhibited an elongated morphology, and peroxisomal marker proteins, such as Pex14p or matrix proteins harboring peroxisomal targeting signal 1, were discernible in a segmented staining pattern, like beads on a string. Endogenous Pex11pβ was also distributed a striped pattern, but which was not coincide with Pex14p and PTS1 matrix proteins. Altered morphology of the lipid membrane was observed when recombinant Pex11p proteins were introduced into proteo-liposomes. Constriction of proteo-liposomes was observed under confocal microscopy and electron microscopy, and the reconstituted Pex11pβ protein localized to the membrane constriction site. Introducing point mutations into the N-terminal amphiphathic helix of Pex11pβ strongly reduced peroxisomal fission, and decreased the oligomer formation. These results suggest that Pex11p contributes to the morphogenesis of the peroxisomal membrane, which is required for subsequent fission by DLP1.

Proliferation and fission of peroxisomes — An update

“…In contrast to classical PBDs, peroxisomal biochemical abnormalities were not detected, but peroxisomes in skin fibroblasts were enlarged and elongated supporting a defect in peroxisome division or proliferation. A proposed function of HsPex11β in matrix protein import (due to mislocalisation of a matrix protein in patient fibroblasts) was not confirmed [190].…”

“…Currently, the number of kinases reported to modulate peroxisomal physiology is limited, and associated kinases or phosphatases have only been reported from plants and fungi. In a systems biology [119,190]. Oligomerisation is required for Pex11β function in membrane elongation and may as well stabilize membrane tubules.…”

“…Pex11β, which is widely expressed in mammalian tissues, has a recognized and important role in peroxisomal growth and division. It remodels and elongates peroxisomal membranes in the initial phase of peroxisomal fission [34,138,190]. This remarkable biophysical property of Pex11β depends on (i) its ability to interact with membrane lipids [11,12,66,190], (ii) amphipathic helices in the N-terminal domain [119] and (iii) self-interaction to form homo-dimeric/oligomeric complexes [11,12,66,190] (Fig.…”

“…2) which are supposed to mediate interaction with membrane phospholipids [66,119]. Deletion of helices or insertion of helix-breaking proline residues inhibits Pex11β-mediated peroxisome elongation and oligomerisation in mammalian cells [11,190] (Figs. 2 & 3).…”

“…Both have been suggested to coordinate and fine-tune peroxisomal growth and division by Pex11 heterodimerisation and interaction with Fis1 and Mff [80,81]. As they cannot (or only partially) complement loss of HsPex11β [39] and exhibit different physiochemical properties [138,190], independent, more specialized functions are likely. Those may be different from the established role in peroxisome division and proliferation.…”