197th ENMC international workshop: Neuromuscular disorders of mitochondrial fusion and fission – OPA1 and MFN2 molecular mechanisms and therapeutic strategies

Mitochondrial and Organellar Crosstalk in Parkinson's Disease

Mitochondrial dysfunction is a well-established pathological event in Parkinson's disease (PD). Proteins misfolding and its impaired cellular clearance due to altered autophagy/mitophagy/pexophagy contribute to PD progression. It has been shown that mitochondria have contact sites with endoplasmic reticulum (ER), peroxisomes and lysosomes that are involved in regulating various physiological processes. In pathological conditions, the crosstalk at the contact sites initiates alterations in intracellular vesicular transport, calcium homeostasis and causes activation of proteases, protein misfolding and impairment of autophagy. Apart from the well-reported molecular changes like mitochondrial dysfunction, impaired autophagy/mitophagy and oxidative stress in PD, here we have summarized the recent scientific reports to provide the mechanistic insights on the altered communications between ER, peroxisomes, and lysosomes at mitochondrial contact sites. Furthermore, the manuscript elaborates on the contributions of mitochondrial contact sites and organelles dysfunction to the pathogenesis of PD and suggests potential therapeutic targets.

Inhibition to DRP1 translocation can mitigate p38 MAPK-signaling pathway activation in GMC induced by hyperglycemia

Diabetic nephropathy (DN) is a serious complication of diabetes with a poorly defined etiology and limited treatment options. Early intervention is a key to preventing the progression of DN. Dynamin-related protein 1 (DRP1) regulates mitochondrial morphology by promoting its fission and is involved in the pathogenesis of numerous diseases. Furthermore, DRP1 is also closely associated with the development of diabetes, but its functional role in DN remains unknown. This study investigated the effect of DRP1 on early stage of DN. DRP1 expression has increased significantly in glomerular mesangial cell (GMC), which is cultivated in high glucose (HG). Ultra-microstructural changes of nephrons, expression of collagen IV and phosph-p38, ROS production, and mitochondrial function were evaluated and, at the same time, were compared with glomerular mesangial cell (GMC) cultured in normal-glucose (NG), mannitol, and a medium with mitochondrial division inhibitor 1 (Midivi-1). Endogenous DRP1 expression increased in DN. Compared to the control groups ofNG and mannitol, overexpression of DRP1 destroyed pathological changes typical of the GMC, like accumulation of extracellular matrix, and an increase in mitochondria division. In addition, Overexpression of DRP1 promoted the activation of p38, the accumulation of ROS, mitochondrial dysfunction, and the synthesis of collagen IV, and all these changes are suppressed by Midivi-1. This study demonstrates that DRP1 overexpression can accelerate pathological changes in the GMC cultured in HG. Further studies are needed to clarify the underlying mechanism of this destructive function.

Novel OPA1 mutation featuring spastic paraparesis and intestinal dysmotility

A 58-year-old man with optic atrophy, spastic paraparesis, axonal sensorimotor peripheral neuropathy and intestinal dysmotility harbors a novel heterozygous missense mutation in the mitochondrial import signal peptide of OPA1. The case underscores the role of OPA1 in the pathogenesis of spastic paraparesis, so far reported only in very few cases, and it adds intestinal dysmotility to the spectrum of adult-onset clinical manifestation of OPA1-associated disease.