Rab32 connects ER stress to mitochondrial defects in multiple sclerosis

J Neuroinflammation. 2017 Jan 23;14(1):19. doi: 10.1186/s12974-016-0788-z.

Abstract

Background: Endoplasmic reticulum (ER) stress is a hallmark of neurodegenerative diseases such as multiple sclerosis (MS). However, this physiological mechanism has multiple manifestations that range from impaired clearance of unfolded proteins to altered mitochondrial dynamics and apoptosis. While connections between the triggering of the unfolded protein response (UPR) and downstream mitochondrial dysfunction are poorly understood, the membranous contacts between the ER and mitochondria, called the mitochondria-associated membrane (MAM), could provide a functional link between these two mechanisms. Therefore, we investigated whether the guanosine triphosphatase (GTPase) Rab32, a known regulator of the MAM, mitochondrial dynamics, and apoptosis, could be associated with ER stress as well as mitochondrial dysfunction.

Methods: We assessed Rab32 expression in MS patient and experimental autoimmune encephalomyelitis (EAE) tissue, via observation of mitochondria in primary neurons and via monitoring of survival of neuronal cells upon increased Rab32 expression.

Results: We found that the induction of Rab32 and other MAM proteins correlates with ER stress proteins in MS brain, as well as in EAE, and occurs in multiple central nervous system (CNS) cell types. We identify Rab32, known to increase in response to acute brain inflammation, as a novel unfolded protein response (UPR) target. High Rab32 expression shortens neurite length, alters mitochondria morphology, and accelerates apoptosis/necroptosis of human primary neurons and cell lines.

Conclusions: ER stress is strongly associated with Rab32 upregulation in the progression of MS, leading to mitochondrial dysfunction and neuronal death.

Keywords: Endoplasmic reticulum; Mitochondria; Multiple sclerosis; Unfolded protein response (UPR).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / physiology
  • Brain / cytology
  • Calnexin / metabolism
  • Cells, Cultured
  • Cytokines / genetics
  • Cytokines / metabolism
  • Encephalomyelitis, Autoimmune, Experimental / pathology
  • Endoplasmic Reticulum Stress / physiology*
  • Female
  • Fetus
  • Humans
  • Male
  • Membrane Glycoproteins / metabolism
  • Mice
  • Middle Aged
  • Mitochondrial Diseases / etiology*
  • Mitochondrial Diseases / pathology
  • Multiple Sclerosis / complications*
  • Multiple Sclerosis / pathology
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism
  • Neurons / metabolism*
  • Neurons / ultrastructure*
  • Transcription Factor CHOP / metabolism
  • Vesicular Transport Proteins / metabolism
  • rab GTP-Binding Proteins / genetics
  • rab GTP-Binding Proteins / metabolism*
  • rab GTP-Binding Proteins / ultrastructure

Substances

  • Cytokines
  • DDIT3 protein, human
  • Membrane Glycoproteins
  • Nerve Tissue Proteins
  • PACS2 protein, human
  • Vesicular Transport Proteins
  • endoplasmin
  • Calnexin
  • Transcription Factor CHOP
  • Rab32 protein, human
  • rab GTP-Binding Proteins

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