The Pex3-Inp1 complex tethers yeast peroxisomes to the plasma membrane.

Georgia E Hulmes,Ewald H Hettema,James M Nuttall,Ellen G Allwood,Noa Dahan,Kathryn R Ayscough,John D Hutchinson

doi:10.1083/jcb.201906021

Georgia E Hulmes, Ewald H Hettema + Show 5 more

Open Access

https://doi.org/10.1083/jcb.201906021

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Abstract

A subset of peroxisomes is retained at the mother cell cortex by the Pex3-Inp1 complex. We identify Inp1 as the first known plasma membrane-peroxisome (PM-PER) tether by demonstrating that Inp1 meets the predefined criteria that a contact site tether protein must adhere to. We show that Inp1 is present in the correct subcellular location to interact with both the plasma membrane and peroxisomal membrane and has the structural and functional capacity to be a PM-PER tether. Additionally, expression of artificial PM-PER tethers is sufficient to restore retention in inp1Δ cells. We show that Inp1 mediates peroxisome retention via an N-terminal domain that binds PI(4,5)P2 and a C-terminal Pex3-binding domain, forming a bridge between the peroxisomal membrane and the plasma membrane. We provide the first molecular characterization of the PM-PER tether and show it anchors peroxisomes at the mother cell cortex, suggesting a new model for peroxisome retention.

Highlights

Eukaryotic cells have evolved molecular mechanisms that control organelle size, number, and position
We demonstrate that Inp1 is a component of the plasma membrane–peroxisome (PM-PER) tether according to the guidelines that define the prerequisites for categorizing a protein as a tether (Eisenberg-Bord et al, 2016), as (1) it is present in the correct subcellular location, apposed to the peroxisome and plasma membranes; (2) Inp1 has the structural capacity to form a PM-PER tether by binding the peroxisomal membrane via a C-terminal Pex3-binding domain and binding the plasma membrane via an N-terminal domain that binds PI(4,5)P2; and (3) Inp1 has the functional capacity to form a PM-PER tether, as an artificial tether that links the peroxisomal membrane to the plasma membrane restores peroxisome retention in inp1Δ cells and overexpression of this minimal tether increases the number of PM-PER contact sites
An artificial tether composed of the plasma membrane–binding PH domain of Num1 artificially attached to peroxisomes is sufficient to restore peroxisome retention in inp1Δ cells

Summary

Introduction

Eukaryotic cells have evolved molecular mechanisms that control organelle size, number, and position. Molecular tethers are required for organelle positioning, multiplication, and establishment of interorganellar contact sites. The balance between organelle tethering and motility determines the intracellular distribution of organelles and their segregation during cell division (Fagarasanu et al, 2010). The Inp1–Pex tethering complex is required for peroxisome retention during cell division and for peroxisome positioning along the mother cortex (Fagarasanu et al, 2005; Knoblach and Rachubinski, 2013; Munck et al, 2009). As has been postulated for other organelles, yeast peroxisomes interact with many cellular structures, including the plasma membrane, ER, vacuole, mitochondria, and lipid bodies (Eisenberg-Bord et al, 2016; Knoblach and Rachubinski, 2019; Wu et al, 2019). Components of some interorganellar peroxisomal contact sites have recently been identified whereas others are still completely uncharacterized, including the plasma membrane–peroxisome (PM-PER) contact site (Shai et al, 2016)

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