Mitochondria and endoplasmic reticulum crosstalk in amyotrophic lateral sclerosis

Abstract

Physical and functional interactions between mitochondria and the endoplasmic reticulum (ER) are crucial for cell life. These two organelles are intimately connected and collaborate to essential processes, such as calcium homeostasis and phospholipid biosynthesis. The connections between mitochondria and endoplasmic reticulum occur through structures named mitochondria associated membranes (MAMs), which contain lipid rafts and a large number of proteins, many of which serve multiple functions at different cellular sites. Growing evidence strongly suggests that alterations of ER-mitochondria interactions are involved in neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS), a devastating and rapidly fatal motor neuron disease. Mutations in proteins that participate in ER-mitochondria interactions and MAM functions are increasingly being associated with genetic forms of ALS and other neurodegenerative diseases. This evidence strongly suggests that, rather than considering the two organelles separately, a better understanding of the disease process can derive from studying the alterations in their crosstalk. In this review we discuss normal and pathological ER-mitochondria interactions and the evidence that link them to ALS.

Keywords: Amyotrophic lateral sclerosis; Calcium; Endoplasmic reticulum; MAMS; Mitochondria; Protein misfolding; Reactive oxygen species.

Figure 1. ER oxidative protein folding could be the hub of multiple pathogenic pathways in ALS

SOD1 misfolding or other ALS-related proteins could cause ER oxidative stress, which could represent a common origin of a multitude of pathogenic pathways that have been identified in ALS, including ER stress, GSH depletion, aberrant calcium handling, protein secretion, and mitochondrial dysfunction.