Biology subjects

Duraine, L.

Publications and source records attributed to Duraine, L..

3 recordsLinked to original sources

bioRxiv2020

Functional interpretation of ATAD3A variants in neuro-mitochondrial phenotypes

BackgroundThe ATPase family AAA-domain containing protein 3A (ATAD3A) is a nuclear-encoded mitochondrial membrane anchored protein involved in diverse processes including mitochondrial dynamics, mitochondrial DNA organization, and cholesterol metabolism. Biallelic deletions (null), recessive missense variants (hypomorph), and heterozygous missense variants or duplications (antimorph) in ATAD3A lead to neurological syndromes in humans. ObjectiveTo expand the mutational spectrum of ATAD3A variants and to provide functional interpretation of missense alleles in trans to deletion alleles. MethodsExome sequencing was used to identify single nucleotide variants (SNVs) and copy number variants (CNVs) in ATAD3A in individuals with neurological and mitochondrial phenotypes. A Drosophila Atad3A Gal4 trap null allele was generated using CRISPR-Cas9 genome editing technology to aid interpretation of variants. ResultsWe report 13 individuals from 8 unrelated families with biallelic ATAD3A variants. Four of the identified missense variants, p.(Leu77Val), p.(Phe50Leu), p.(Arg170Trp), p.(Gly236Val), were inherited in trans to loss-of-function alleles. A fifth missense variant, p.(Arg327Pro), was homozygous. Affected individuals exhibited findings previously associated with ATAD3A pathogenic variation, including developmental delay, hypotonia, congenital cataracts, hypertrophic cardiomyopathy, and cerebellar atrophy. Drosophila studies indicated that Phe50Leu, Gly236Val, and Arg327Pro are severe loss-of-function alleles leading to early developmental lethality and neurogenesis defects, whereas Leu77Val and Arg170Trp are partial loss of function alleles that cause progressive locomotion defects. Moreover, Leu77Val and Arg170Trp expression leads to an increase in autophagy and mitophagy in adult muscles. ConclusionOur findings expand the allelic spectrum of ATAD3A variants, and exemplify the use of a functional assay in Drosophila to aid variant interpretation.

genetics↗

bioRxiv2020

Lysosomal nucleotide metabolism regulates ER proteostasis through mTOR signaling

Organelles in eukaryotic cells are compartmentalized to carry out different functions, and require specific mechanisms governing their coordination. Two of these organelles, the lysosome and the endoplasmic reticulum (ER), play crucial roles in regulating cellular homeostasis and organismal health. The lysosome contains various enzymes devoted to the hydrolysis of specific substrates, and dysfunctions of these hydrolases and their related metabolic processes are implicated in many diseases 1. On the other hand, ER is essential for protein synthesis and utilizes quality control mechanisms to maintain proteostasis. The metabolic status of the lysosome is now known to actively influence nuclear transcription and mitochondrial signaling 2-4. However, whether and how mechanistically lysosomal metabolic activities regulate ER proteostasis remain unclear. Here, we reported that RSH-1, the Caenorhabditis elegans RelA/SpoT Homolog (RSH) protein, carries a lysosomal NADPH phosphatase activity and acts through the mammalian/mechanistic target of rapamycin (mTOR) signaling to regulate ER proteostasis. We discovered that RSH-1 is localized to the lysosome. Its mutation reduces NADPH hydrolysis by the lysosome, leading to a protection against ER stress-induced lethality. We further revealed that this ER stress tolerance requires lysosomal vacuolar-type H+-ATPase (v-ATPase), and Rag GTPases and ribosomal protein S6 kinase (S6K) in the mTOR signaling pathway. Through transcriptome analysis, we discovered that the S6K activation by the RSH-1 mutation increases the basal expression of X-box binding protein 1 (XBP-1) and peptidyl-prolyl cis-trans isomerases, which is necessary for improving ER proteostasis. Moreover, we demonstrated the lysosomal localization of RSH-1 mammalian homolog and its conserved role in regulating mTOR signaling. Together, our findings reveal the key role of a specific lysosomal nucleotide hydrolase in regulating organellar coordination and also signaling mechanisms underlying this active regulation, and suggest that diseases resulted from deficiency in lysosomal hydrolases may be attributed to the distortion of signal transduction and organelle homeostasis.

cell biology↗

bioRxiv2019

NFIA regulates granule recruitment and exocytosis in the adult pancreas

After food ingestion, pancreatic cells secrete zymogen and hormone-containing granules to precisely control digestion and blood glucose levels. Identifying regulators of this process is paramount to combatting multiple pancreatic diseases. Here we show that pancreatic deletion of the transcription factor nuclear factor IA (NFIA) leads to hyperglycemia, hypoinsulinemia, and hypolipidemia. Surprisingly, insulin and digestive enzymes are produced in the absence of NFIA, however, they are not secreted properly and instead accumulate inside pancreatic cells. In NFIA-deficient mice we saw a reduction of insulin granules in the ready releasable pool and the first-phase insulin response was impaired. We found that NFIA binds to and activates Rab39b, a Rab GTPase critical for exocytosis. Re-expression of Rab39b in NFIA knockout islets restored glucose-stimulated insulin secretion. In sum, the NFIA-Rab39b axis regulates pancreatic physiology through granule recruitment and docking, linking NFIA to a new process with potential effects in diabetes, pancreatitis, and lipid disorders.

cell biology↗