Biology subjects

Nishino, I.

Publications and source records attributed to Nishino, I..

3 recordsLinked to original sources

bioRxiv2021

Imaging-based evaluation of pathogenicity by novel DNM2 variants associated with centronuclear myopathy

Centronuclear myopathy (CNM) is characterized clinically by muscle weakness and pathologically by the presence of centralized nuclei and disarrangement of T-tubules in muscle fibers. DNM2 which encodes a large GTPase dynamin 2 have been identified as a causative gene for CNM. Nevertheless, the identification of DNM2 variants may not always lead to the definitive diagnosis as their pathogenicity is often unknown. In this study, by imaging T-tubule-like structures reconstituted in cellulo, we demonstrated that aberrant membrane remodeling by mutant dynamin 2 is tightly associated with gain-of-function features of DNM2 variants. This simple in cellulo assay provided quantitative data required for accurately evaluating pathogenicity of reported and novel DNM2 variants identified from CNM patients in our cohort. Our approaches combining the in cellulo assay with clinical information of the patients enabled to explain the course of a disease progression by pathogenesis of each variant in DNM2-associated CNM.

cell biology↗

bioRxiv2020

Direct uptake mechanism in lysosome required for neuromuscular homeostasis

The degradation of cellular components plays an essential role in homeostasis. However, the known degradation pathways cannot account for the levels of proteolysis in cells. Here, we demonstrate that cytosolic proteins are imported into lysosomes in an ATP-dependent manner for degradation through a direct uptake mechanism distinct from any known pathway. SIDT2, a lysosomal membrane protein previously reported as an RNA transporter, translocates substrate proteins across the lysosomal membrane. Furthermore, we identify a dominant-negative mutation in SIDT2 that causes neuropathy and distal myopathy with rimmed vacuoles, a protein aggregation disease in humans. We generate Sidt2 knockout mice, recapitulating the characteristic features of this disease. Our results reveal a novel degradation pathway and illustrate its crucial role in cellular proteostasis, physiology, and pathophysiology. One Sentence SummaryDiscovery of a novel proteolytic pathway in cells, the dysfunction of which leads to protein aggregation disease in humans.

cell biology↗

bioRxiv2020

A novel saline-soluble, rapidly-metabolized RyR1 inhibitor rescues volatile anesthesia-induced death and environmental heat stroke in a mouse model relevant to malignant hyperthermia

Mutations in the type 1 ryanodine receptor (RyR1), a Ca2+ release channel in skeletal muscle, hyperactivate the channel to cause malignant hyperthermia (MH) and are implicated in severe heat stroke. Dantrolene, the only approved drug for MH, has the disadvantages of having very poor water solubility and long plasma half-life. We show here that a novel RyR1-selective inhibitor, 6,7-(methylenedioxy)-1-octyl-4-quinolone-3-carboxylic acid (Compound 1, Cpd1), effectively prevents and treats MH and heat stroke in several mouse models relevant to MH. Cpd1 reduced resting intracellular Ca2+, inhibited halothane- and isoflurane-induced Ca2+ release, suppressed caffeine-induced contracture in skeletal muscle, reduced sarcolemmal cation influx, and prevented or reversed the fulminant MH crisis induced by isoflurane anesthesia and rescued animals from heat stroke caused by environmental heat stress. Notably, Cpd1 has great advantages of better water solubility and rapid clearance in vivo over dantrolene. Cpd1 has the potential to be a promising new candidate for effective treatment of patients carrying RyR1 mutations.

pharmacology and toxicology↗