Expression of a T39N mutant Rab32 protein arrests mitochondria movement within neurites of differentiated SH-SY5Y cells

Abstract

We have shown that multiple sclerosis (MS) and endoplasmic reticulum (ER) stress induce Rab32, an ER/mitochondria-localized small GTPase. High levels of both dominant-active (Q85L) or dominant-inactive (T39N) Rab32 are toxic to neurons. While Rab32Q85L interacts with its effector Drp1 to promote mitochondria fission, it is unclear how Rab32T39N could result as toxic to neurons. Given the perinuclear clustering of mitochondria observed upon transfection of inactive Rab32, we hypothesized Rab32T39N could stall mitochondria within neurites. The movement of mitochondria depends on kinesin-binding Miro proteins. High cytosolic [Ca] is bound by an EF hand motif within Miro proteins, resulting in mitochondrial arrest. Consistent with increased cytosolic [Ca], expression of Rab32T39N arrests mitochondria movement within neurites.

Nuclear and Cytoplasmatic Players in Mitochondria-Related CNS Disorders: Chromatin Modifications and Subcellular Trafficking

“…The authors suggested inhibition of Rab32 production could inhibit neurodegeneration in vivo. Moreover, Rab32 is also involved in the direct trafficking of mitochondria around the cell, as overexpression of a constitutively inactive form of Rab32 was shown to slow down the mitochondrial movement towards neurites in SH-SY5Y cells [183]. Since defects in mitochondrial axonal transport are known to be an early sign of neuroinflammation, it is possible that overexpression of Rab32 in MS acts as a global negative factor for neuronal mitochondria [183,184].…”

“…Moreover, Rab32 is also involved in the direct trafficking of mitochondria around the cell, as overexpression of a constitutively inactive form of Rab32 was shown to slow down the mitochondrial movement towards neurites in SH-SY5Y cells [183]. Since defects in mitochondrial axonal transport are known to be an early sign of neuroinflammation, it is possible that overexpression of Rab32 in MS acts as a global negative factor for neuronal mitochondria [183,184]. In a study aimed to identify novel CpG sites the methylation of which might be correlated to the chronological and biological age, individuals exhibiting methylation levels of the RAB32 CpG site higher than 10% were observed to be more prone to disability than people with lower levels, providing the first evidence that epigenetic modifications of genes involved in mitochondrial quality control occur over time according to the aging decline [185].…”

Mitochondrial a Kinase Anchor Proteins in Cardiovascular Health and Disease: A Review Article on Behalf of the Working Group on Cellular and Molecular Biology of the Heart of the Italian Society of Cardiology

“…RAB32 anchors PKA and promotes Drp1 phosphorylation on Serine 656, in turn inactivating Drp1, inhibiting apoptosis and promoting mitochondrial fusion [ 38 , 81 ]. In addition, RAB32 has been involved in mitochondrial movements within neurites [ 39 ] and mitochondrial uptake of cytoplasmic proteins during ageing [ 40 ]. A recent study also localizes RAB32 in lysosomes, wherein it regulates metabolism and cell growth by the mTORC1 pathway [ 38 ].…”

Proteolysis of Rab32 by Salmonella GtgE induces an inactive GTPase conformation

“…Rab32 has multiple functions in the cell. It is involved in the biogenesis of lysosome-related organelles, autophagy, mitochondrial dynamics and regulates phagosome maturation during bacterial invasion (Raposo et al, 2001;Alto et al, 2002;Holt et al, 2006;Wasmeier et al, 2006;Raposo and Marks, 2007;Benado et al, 2009;Bultema et al, 2012;Ao et al, 2014;Haile et al, 2017;Rybnicek et al, 2018;Hu et al, 2019). Moreover, in a recent study, Rab32 has been shown to facilitate the delivery of itaconate, a mitochondrial metabolite with antimicrobial activity, into the Salmonella-containing vacuoles (SCVs), thereby restricting the replication of Salmonella (Chen et al, 2020).…”