Growing evidence emphasizes insufficient clearance of pathological alpha-synuclein (alpha SYN) aggregates in the progression of Parkinson's disease (PD). Consequently, cellular degradation pathways represent a potential therapeutic target. Prolyl oligopeptidase (PREP) is highly expressed in the brain and has been suggested to increase alpha SYN aggregation and negatively regulate the autophagy pathway. Inhibition of PREP with a small molecule inhibitor, KYP-2407, stimulates autophagy and reduces the oligomeric species of alpha SYN aggregates in PD mouse models. However, whether PREP inhibition has any effects on intracellular alpha SYN fibrils has not been studied before. In this study, the effect of KYP2407 on alpha SYN preformed fibrils (PFFs) was tested in SH-SY5Y cells and human astmcytes. Immunostaining analysis revealed that both cell types accumulated alpha SYN PFFs intracellularly but KYP-2047 decreased intracellular alpha SYN deposits only in SH-SY5Y cells, as astrocytes did not show any PREP activity. Western blot analysis confirmed the reduction of high molecular weight alpha SYN species in SH-SY5Y cell lysates, and secretion of aSYN from SH-SY5Y cells also decreased in the presence of KYP-2407. Accumulation of alpha SYN inside the SH-SY5Y cells resulted in an increase of the auto-lysosomal proteins p62 and LC3BII, as well as calpain 1 and 2, which have been shown to be associated with PD pathology. Notably, treatment with KYP-2407 significantly reduced p62 and LC3BII levels, indicating an increased autophagic flux, and calpain 1 and 2 levels returned to normal in the presence of KYP-2407. Our findings indicate that PREP inhibition can potentially be used as therapy to reduce the insoluble intracellular alpha SYN aggregates.

Tibial muscular dystrophy (TMD) is the first described human titinopathy. It is a mild adult-onset slowly progressive myopathy causing weakness and atrophy in the anterior lower leg muscles. TMD is caused by mutations in the last two exons, Mex5 and Mex6, of the titin gene (TTN). The first reported TMD mutations were dominant, but the Finnish founder mutation FINmaj, an 11-bp insertion/deletion in Mex6, in homozygosity caused a completely different severe early-onset limb-girdle muscular dystrophy 2J (LGMD2J). Later, we reported that not all TMD mutations cause LGMD when homozygous or compound heterozygous with truncating mutation, but some of them rather cause a more severe TMD-like distal disease. We have now performed targeted next-generation sequencing of myopathy-related genes on seven families from Albania, Bosnia, Iran, Tunisia, Belgium, and Spain with juvenile or early adult onset recessive distal myopathy. Novel mutations in TTN Mex5, Mex6 and A-band exon 340 were identified in homozygosity or compound heterozygosity with a frameshift or nonsense mutation in TTN I- or A-band region. Family members having only one of these TTN mutations were healthy. Our results add yet another entity to the list of distal myopathies: juvenile or early adult onset recessive distal titinopathy.