Biology subjects

Sei, Y.

Publications and source records attributed to Sei, Y..

4 recordsLinked to original sources

bioRxiv2024

CHCHD2 mutant mice display mitochondrial protein accumulation and disrupted energy metabolism

Mutations in the mitochondrial cristae protein CHCHD2 lead to a late-onset autosomal dominant form of Parkinsons disease (PD) which closely resembles idiopathic PD, providing the opportunity to gain new insights into the mechanisms of mitochondrial dysfunction contributing to PD. To begin to address this, we used CRISPR genome-editing to generate CHCHD2 T61I point mutant mice. CHCHD2 T61I mice had normal viability, and had only subtle motor deficits with no signs of premature dopaminergic (DA) neuron degeneration. Nonetheless, CHCHD2 T61I mice exhibited robust molecular changes in the brain including increased CHCHD2 insolubility, accumulation of CHCHD2 protein preferentially in the substantia nigra (SN), and elevated levels of -synuclein. Metabolic analyses revealed an increase in glucose metabolism through glycolysis relative to the TCA cycle with increased respiratory exchange ratio, and immune-electron microscopy revelated disrupted mitochondria in DA neurons. Moreover, spatial genomics revealed decreased expression of mitochondrial complex I and III respiratory chain proteins, while proteomics revealed increased respiratory chain and other mitochondrial protein-protein interactions. As such, the CHCHD2 T61I point-mutation mice exhibit robust mitochondrial disruption and a consequent metabolic shift towards glycolysis. These findings thus establish CHCHD2 T61I mice as a new model for mitochondrial-based PD, and implicate disrupted respiratory chain function as a likely causative driver.

neuroscience↗

bioRxiv2024

Chronic hyperactivation of midbrain dopamine neurons causes preferential dopamine neuron degeneration

Parkinsons disease (PD) is characterized by the death of substantia nigra (SNc) dopamine (DA) neurons, but the pathophysiological mechanisms that precede and drive their death remain unknown. The activity of DA neurons is likely altered in PD, but we understand little about if or how chronic changes in activity may contribute to degeneration. To address this question, we developed a chemogenetic (DREADD) mouse model to chronically increase DA neuron activity, and confirmed this increase using ex vivo electrophysiology. Chronic hyperactivation of DA neurons resulted in prolonged increases in locomotor activity during the light cycle and decreases during the dark cycle, consistent with chronic changes in DA release and circadian disturbances. We also observed early, preferential degeneration of SNc projections, recapitulating the PD hallmarks of selective vulnerability of SNc axons and the comparative resilience of ventral tegmental area axons. This was followed by eventual loss of midbrain DA neurons. Continuous DREADD activation resulted in a sustained increase in baseline calcium levels, supporting a role for increased calcium in the neurodegeneration process. Finally, spatial transcriptomics from DREADD mice examining midbrain DA neurons and striatal targets, and cross-validation with human patient samples, provided insights into potential mechanisms of hyperactivity-induced toxicity and PD. Our results thus reveal the preferential vulnerability of SNc DA neurons to increased neural activity, and support a potential role for increased neural activity in driving degeneration in PD.

neuroscience↗

bioRxiv2021

In vivo CRISPRi screen reveals the differential requirement for mitochondrial respiratory chain function between in vivo and in vitro tumor growth

The Warburg effect, aerobic glycolysis, is a hallmark feature of cancer cells grown in culture. However, the relative roles of glycolysis and respiratory metabolism in supporting in vivo tumor growth and significant processes such as tumor dissemination and metastases remain poorly understood, particularly on a systems level. Using a CRISPRi mini-library enriched for mitochondrial ribosomal protein and respiratory chain genes in multiple human lung cancer cell lines we analyzed in vivo metabolic requirements in xenograft tumors grown in distinct anatomic contexts. While knockdown of mitochondrial ribosomal protein and respiratory chain genes (mito-respiratory genes) has little impact on growth in vitro, tumor cells depend heavily on these genes when grown in vivo as either flank or primary orthotopic lung tumor xenografts. In contrast, respiratory function is comparatively dispensable for metastatic tumor growth. RNA-Seq and metabolomics analysis of tumor cells expressing individual sgRNAs against mito-respiratory genes indicate overexpression of glycolytic genes and increased sensitivity of glycolytic inhibition compared to control when grown in vitro, but when grown in vivo as primary tumors these cells downregulate glycolytic mechanisms. These studies demonstrate that discrete perturbations of mitochondrial metabolism impact in vivo tumor growth in a context-specific manner and provides systems-level evidence that respiratory function modulates tumor growth in vivo, suggesting that ATP limits growth and metastatic potential.

cancer biology↗

bioRxiv2020

Loss of PI3-kinase activity of inositol polyphosphate multikinase impairs PDK1-mediated AKT activation, cell migration, and intestinal homeostasis

Inositol polyphosphate multikinase (IPMK) is a rate-limiting enzyme in the inositol phosphate (IP) pathway which converts IP3 to IP4 and IP5. In mammalian cells, IPMK can also act as a phosphoinositol-3-kinase (PI3-kinase). We previously found that IPMK is a critical PI3-kinase activator of AKT. Here, we show that IPMK mediates AKT activation by promoting membrane localization and activation of PDK1. The PI3-kinase activity of IPMK is dispensable for membrane localization of AKT, which is entirely controlled by classical PI3-kinase (p110,{beta},{gamma} , {delta}). By contrast, we found that PDK1 membrane localization was largely independent of classical PI3-kinase. Membrane localization of PDK1 stimulates cell migration by dissociating ROCK1 from inhibitory binding to RhoE and promoting ROCK1-mediated myosin light chain (MLC) phosphorylation. Deletion of IPMK impairs cell migration associated with the abolition of PDK1-mediated ROCK1 disinhibition and subsequent MLC phosphorylation. To investigate the physiological relevance of IPMK-mediated AKT activation, we generated mice selectively lacking IPMK in epithelial cells of the intestine, where IPMK is highly expressed. Deletion of IPMK in intestinal epithelial cells markedly reduced AKT phosphorylation and diminished numbers of Paneth cells - a crypt-resident epithelial cell type that generates the physiological niche for intestinal stem cells. Ablation of IPMK impaired intestinal epithelial cell regeneration basally and after; chemotherapy-induced damage, suggesting a broad role for IPMK in the activation of AKT and intestinal tissue regeneration. In summary, the PI3-kinase activity of IPMK promotes membrane localization of PDK1, a critical kinase whereby AKT maintains intestinal homeostasis. One Sentence SummaryPI3-kinase activity of IPMK is essential for activation of AKT.

cell biology↗