Defective recruitment of motor proteins to autophagic compartments contributes to autophagic failure in aging.

Eloy Bejarano,David Yin,Ana Maria Cuervo,John W Murray,Andrea Yuste,Xintao Wang,Allan W Wolkoff,Olatz Pampliega,Bindi Patel

doi:10.1111/acel.12777

Abstract

SummaryInability to preserve proteostasis with age contributes to the gradual loss of function that characterizes old organisms. Defective autophagy, a component of the proteostasis network for delivery and degradation of intracellular materials in lysosomes, has been described in multiple old organisms, while a robust autophagy response has been linked to longevity. The molecular mechanisms responsible for defective autophagic function with age remain, for the most part, poorly characterized. In this work, we have identified differences between young and old cells in the intracellular trafficking of the vesicular compartments that participate in autophagy. Failure to reposition autophagosomes and lysosomes toward the perinuclear region with age reduces the efficiency of their fusion and the subsequent degradation of the sequestered cargo. Hepatocytes from old mice display lower association of two microtubule‐based minus‐end‐directed motor proteins, the well‐characterized dynein, and the less‐studied KIFC3, with autophagosomes and lysosomes, respectively. Using genetic approaches to mimic the lower levels of KIFC3 observed in old cells, we confirmed that reduced content of this motor protein in fibroblasts leads to failed lysosomal repositioning and diminished autophagic flux. Our study connects defects in intracellular trafficking with insufficient autophagy in old organisms and identifies motor proteins as a novel target for future interventions aiming at correcting autophagic activity with anti‐aging purposes.

Highlights

Autophagy is a highly conserved catabolic process responsible for the delivery of cytoplasmic materials into lysosomes for their degradation (Galluzzi et al, 2017; Levine & Klionsky, 2017)
Since the role of the minus-end-directed motor dynein in retrograde APG trafficking has been well stablished (Jahreiss et al, 2008) and lysosome-associated KIFC2 did not significantly change with age (Figure 4e,f) and was almost absent in primary fibroblasts (Figure S3d), we set instead to understand the contribution of KIFC3 to the agingautophagy phenotype because (i) we found that KIFC3 was highly enriched in purified lysosomes (Figure 4f), (ii) its levels were markedly reduced in this compartment in liver from old mice (Figure 4f), and (iii) starvation, at least partially, restored KIFC3 levels in lysosomes (Figure 4f)
We found reduced displacement of lysosomal vesicles but not of APG in KIFC3 (À) cells when compared with control (Figure 5d,e)

Summary

| INTRODUCTION

Autophagy is a highly conserved catabolic process responsible for the delivery of cytoplasmic materials (proteins and organelles) into lysosomes for their degradation (Galluzzi et al, 2017; Levine & Klionsky, 2017). Subcellular positioning of organelles is mainly determined by the microtubule network and the localization of autophagic and lysosomal compartments is not an exception (Mackeh, Perdiz, Lorin, Codogno & Pous, 2013; Monastyrska, Rieter, Klionsky & Reggiori, 2009) Interaction of these vesicles with microtubules is mediated by motor proteins that provide the force necessary to move them along the tubulin tracks. We show that defective association with minus-end-directed motor proteins by autophagic compartments, autophagosomes and lysosomes, might be a driver of the decline of autophagy with age. The motor defect seems to preferentially affect basal quality control autophagy whereas induction of autophagy by starvation restores in part association of specific motor proteins with autophagosomes and lysosomes These findings highlight the feasibility of activating inducible autophagy in old organisms to compensate for their defective basal autophagy

| RESULTS

| DISCUSSION

Findings

| EXPERIMENTAL PROCEDURES

CONFLICT OF INTERESTS