ER calcium depletion as a key driver for impaired ER-to-mitochondria calcium transfer and mitochondrial dysfunction in Wolfram syndrome.

Wolfram syndrome is a rare genetic disease caused by mutations in the WFS1 or CISD2 gene. A primary defect in Wolfram syndrome involves poor ER Ca handling, but how this disturbance leads to the disease is not known. The current study, performed in primary neurons, the most affected and disease-relevant cells, involving both Wolfram syndrome genes, explains how the disturbed ER Ca handling compromises mitochondrial function and affects neuronal health.

The Expression of RAAS Key Receptors, and , Is Downregulated at an Early Stage in a Rat Model of Wolfram Syndrome.

Wolfram syndrome (WS) 1 is a rare monogenic neurodegenerative disorder caused by mutations in the gene encoding WFS1. Knowledge of the pathophysiology of WS is incomplete and to date, there is no treatment available. Here, we describe early deviations in the renin-angiotensin-aldosterone system (RAAS) and bradykinin pathway (kallikrein kinin system, KKS) observed in a rat model of WS ( KO) and the modulative effect of glucagon-like peptide-1 receptor agonist liraglutide (LIR) and anti-epileptic drug valproate (VPA), which have been proven effective in delaying WS progression in WS animal models.

A novel role of KEAP1/PGAM5 complex: ROS sensor for inducing mitophagy.

When ROS production exceeds the cellular antioxidant capacity, the cell needs to eliminate the defective mitochondria responsible for excessive ROS production. It has been proposed that the removal of these defective mitochondria involves mitophagy, but the mechanism of this regulation remains unclear. Here, we demonstrate that moderate mitochondrial superoxide and hydrogen peroxide production oxidates KEAP1, thus breaking the interaction between this protein and PGAM5, leading to the inhibition of its proteasomal degradation.

Miro proteins prime mitochondria for Parkin translocation and mitophagy.

The Parkinson's disease-associated protein kinase PINK1 and ubiquitin ligase Parkin coordinate the ubiquitination of mitochondrial proteins, which marks mitochondria for degradation. Miro1, an atypical GTPase involved in mitochondrial trafficking, is one of the substrates tagged by Parkin after mitochondrial damage. Here, we demonstrate that a small pool of Parkin interacts with Miro1 before mitochondrial damage occurs.

Compound heterozygous SPATA5 variants in four families and functional studies of SPATA5 deficiency.

Variants in the SPATA5 gene were recently described in a cohort of patients with global developmental delay, sensorineural hearing loss, seizures, cortical visual impairment and microcephaly. SPATA5 protein localizes predominantly in the mitochondria and is proposed to be involved in mitochondrial function and brain developmental processes. However no functional studies have been performed.

Role of Mitochondrial Dynamics in Neuronal Development: Mechanism for Wolfram Syndrome.

Deficiency of the protein Wolfram syndrome 1 (WFS1) is associated with multiple neurological and psychiatric abnormalities similar to those observed in pathologies showing alterations in mitochondrial dynamics. The aim of this study was to examine the hypothesis that WFS1 deficiency affects neuronal function via mitochondrial abnormalities. We show that down-regulation of WFS1 in neurons leads to dramatic changes in mitochondrial dynamics (inhibited mitochondrial fusion, altered mitochondrial trafficking, and augmented mitophagy), delaying neuronal development.

Mitochondrial biogenesis is required for axonal growth.

During early development, neurons undergo complex morphological rearrangements to assemble into neuronal circuits and propagate signals. Rapid growth requires a large quantity of building materials, efficient intracellular transport and also a considerable amount of energy. To produce this energy, the neuron should first generate new mitochondria because the pre-existing mitochondria are unlikely to provide a sufficient acceleration in ATP production.

BECN1 is involved in the initiation of mitophagy: it facilitates PARK2 translocation to mitochondria.

The autophagy protein BECN1/Beclin 1 is known to play a central role in autophagosome formation and maturation. The results presented here demonstrate that BECN1 interacts with the Parkinson disease-related protein PARK2. This interaction does not require PARK2 translocation to mitochondria and occurs mostly in cytosol.

Principles of the mitochondrial fusion and fission cycle in neurons.

Mitochondrial fusion-fission dynamics play a crucial role in many important cell processes. These dynamics control mitochondrial morphology, which in turn influences several important mitochondrial properties including mitochondrial bioenergetics and quality control, and they appear to be affected in several neurodegenerative diseases. However, an integrated and quantitative understanding of how fusion-fission dynamics control mitochondrial morphology has not yet been described.