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- ItemA Homozygous PPP1R21 Splice Variant Associated with Severe Developmental Delay, Absence of Speech, and Muscle Weakness Leads to Activated Proteasome Function(Totowa, NJ : Humana Press, 2023) Hentschel, Andreas; Meyer, Nancy; Kohlschmidt, Nicolai; Groß, Claudia; Sickmann, Albert; Schara-Schmidt, Ulrike; Förster, Fabian; Töpf, Ana; Christiansen, Jon; Horvath, Rita; Vorgerd, Matthias; Thompson, Rachel; Polaparapu, Kiran; Lochmüller, Hanns; Preusse, Corinna; Hannappel, Luis; Schänzer, Anne; Grüneboom, Anika; Gangfuß, Andrea; Roos, AndreasPPP1R21 acts as a co-factor for protein phosphatase 1 (PP1), an important serine/threonine phosphatase known to be essential for cell division, control of glycogen metabolism, protein synthesis, and muscle contractility. Bi-allelic pathogenic variants in PPP1R21 were linked to a neurodevelopmental disorder with hypotonia, facial dysmorphism, and brain abnormalities (NEDHFBA) with pediatric onset. Functional studies unraveled impaired vesicular transport as being part of PPP1R21-related pathomechanism. To decipher further the pathophysiological processes leading to the clinical manifestation of NEDHFBA, we investigated the proteomic signature of fibroblasts derived from the first NEDHFBA patient harboring a splice-site mutation in PPP1R21 and presenting with a milder phenotype. Proteomic findings and further functional studies demonstrate a profound activation of the ubiquitin–proteasome system with presence of protein aggregates and impact on cellular fitness and moreover suggest a cross-link between activation of the proteolytic system and cytoskeletal architecture (including filopodia) as exemplified on paradigmatic proteins including actin, thus extending the pathophysiological spectrum of the disease. In addition, the proteomic signature of PPP1R21-mutant fibroblasts displayed a dysregulation of a variety of proteins of neurological relevance. This includes increase proteins which might act toward antagonization of cellular stress burden in terms of pro-survival, a molecular finding which might accord with the presentation of a milder phenotype of our NEDHFBA patient.
- ItemFYCO1 Increase and Effect of Arimoclomol–Treatment in Human VCP–Pathology(Basel : MDPI, 2022) Guettsches, Anne-Katrin; Meyer, Nancy; Zahedi, René P.; Evangelista, Teresinha; Muentefering, Thomas; Ruck, Tobias; Lacene, Emmanuelle; Heute, Christoph; Gonczarowska-Jorge, Humberto; Schoser, Benedikt; Krause, Sabine; Hentschel, Andreas; Vorgerd, Matthias; Roos, AndreasDominant VCP–mutations cause a variety of neurological manifestations including inclusion body myopathy with early–onset Paget disease and frontotemporal dementia 1 (IBMPFD). VCP encodes a ubiquitously expressed multifunctional protein that is a member of the AAA+ protein family, implicated in multiple cellular functions ranging from organelle biogenesis to ubiquitin–dependent protein degradation. The latter function accords with the presence of protein aggregates in muscle biopsy specimens derived from VCP–patients. Studying the proteomic signature of VCP–mutant fibroblasts, we identified a (pathophysiological) increase of FYCO1, a protein involved in autophagosome transport. We confirmed this finding applying immunostaining also in muscle biopsies derived from VCP–patients. Treatment of fibroblasts with arimoclomol, an orphan drug thought to restore physiologic cellular protein repair pathways, ameliorated cellular cytotoxicity in VCP–patient derived cells. This finding was accompanied by increased abundance of proteins involved in immune response with a direct impact on protein clearaqnce as well as by elevation of pro–survival proteins as unravelled by untargeted proteomic profiling. Hence, the combined results of our study reveal a dysregulation of FYCO1 in the context of VCP–etiopathology, highlight arimoclomol as a potential drug and introduce proteins targeted by the pre–clinical testing of this drug in fibroblasts.