Sheshadri, P. | Search bioRxiv

bioRxiv2022

Deubiquitinase USP1 influences the dedifferentiation of mouse pancreatic β-cells

Diabetes is a metabolic disease caused majorly due to loss of insulin secreting {beta}-cells. Along with apoptosis, recent reports revealed dedifferentiation to be the added reason for the reduced {beta}-cell mass. The Ubiquitin Proteasome system comprising of E3 ligase and deubiquitinases (DUBs) control several key aspects of pancreatic {beta}-cell functions. The role of deubiquitinases in orchestrating the dedifferentiation process in several cancers have been well deciphered, but its role in dedifferentiation of pancreatic {beta}-cells remains elusive. In this study, screening for key DUBs that regulate dedifferentiation, identified USP1 to be specifically involved in the process. Inhibition of USP1 either by genetic intervention or small molecule inhibitor ML323 restored epithelial phenotype of {beta}-cells, but not with inhibition of other DUBs. Conversely overexpression of USP1 was sufficient to dedifferentiate {beta}-cells, even in absence of dedifferentiation inducing cues. Mechanistic insight showed USP1 to probably mediate its effect via modulating the expression of Inhibitor of Differentiation (ID) 2. Further, in an in vivo streptozotocin (STZ) induced dedifferentiation mouse model system, treatment with ML323 rescued the hyperglycaemic state. Overall, this study assigns a novel role to USP1 in dedifferentiation of {beta}-cells and its inhibition may have a therapeutic application of reducing the {beta}-cell loss during diabetes.

cell biology↗

bioRxiv2020

Paradoxical neuronal hyperexcitability in a mouse model of mitochondrial pyruvate import deficiency

Neuronal excitation imposes a high demand of ATP in neurons. Most of the ATP derives primarily from pyruvate-mediated oxidative phosphorylation, a process that relies on import of pyruvate into mitochondria occuring exclusively via the mitochondrial pyruvate carrier (MPC). To investigate whether deficient oxidative phosphorylation impacts neuron excitability, we generated a mouse strain carrying a conditional deletion of MPC1, an essential subunit of the mitochondrial pyruvate carrier, specifically in adult glutamatergic neurons. We found that, despite decreased levels of oxidative phosphorylation in these excitatory neurons, mice were normal at rest. Paradoxically, in response to mild inhibition of GABA mediated synaptic activity, they rapidly developed severe seizures and died, whereas under similar conditions the behaviour of control mice remained unchanged. We show that neurons with a deficient MPC are intrinsically hyperexcitable as a consequence of impaired calcium homeostasis, which reduces M-type potassium channel activity. Provision of ketone bodies restores energy status, calcium homeostasis and M-channel activity and attenuates seizures in animals fed a ketogenic diet. Our results provide an explanation for the paradoxical seizures that frequently accompany a large number of neuropathologies, including cerebral ischemia and diverse mitochondriopathies, in which neurons experience an energy deficit. One Sentence SummaryDecreased OXPHOS and Ca2+-mediated neuronal hyperexcitability lead to seizure in a mouse model of mitochondrial pyruvate import deficiency.

neuroscience↗