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Biology subjects

Hezzaz, S.

Publications and source records attributed to Hezzaz, S..

2 recordsLinked to original sources

Released mitochondrial DNA and neurofilament light chain as Parkinson's disease phenotypes in patient-specific midbrain assembloids

Parkinsons Disease is the second most common neurodegenerative disorder worldwide, with growing numbers and considerable societal and economic concerns. Human cell culture systems are efficient models for neurodegenerative disorders and allow for personalized, non-invasive analysis of cellular and molecular disease mechanisms. Midbrain organoids and assembloids are advanced 3D culture systems that recapitulate the human midbrain, which is highly affected by Parkinsons disease. Here, we used healthy control and patient-specific midbrain assembloids to assess mitochondrial DNA phenotypes and NfL levels alongside neurodegeneration and alpha-synuclein phosphorylation. Importantly, alterations in mitochondrial DNA homeostasis and NfL levels can be assayed in the supernatant and therefore are particularly suitable as biomarkers and for high throughput screening approaches.

neuroscience↗

Vitamin K-dependent carboxylation of junctate regulates calcium flux and adaptation to metabolic stress in β-cells

Vitamin K is a micronutrient necessary for the {gamma}-carboxylation of glutamic acids. This post-translational modification occurs in the endoplasmic reticulum (ER) and affects secreted proteins. Clinical studies have recently implicated vitamin K in the pathophysiology of diabetes, but the underlying molecular mechanism remains unknown. Here, we show that mouse {beta}-cells lacking {gamma}-carboxylation fail to adapt their insulin secretion in the context of age-related insulin resistance or diet-induced {beta}-cell stress. In human islets, {gamma}-carboxylase expression positively correlates with improved insulin secretion in response to glucose. We identified Endoplasmic Reticulum Gla Protein (ERGP) as a novel {gamma}-carboxylated ER-resident calcium-binding protein expressed in {beta}-cells. Mechanistically, {gamma}-carboxylation of ERGP protects cells against calcium overfilling by diminishing STIM1 and Orai1 interaction and restraining store-operated calcium entry. These results reveal a critical role for vitamin K-dependent {gamma}-carboxylation in the regulation of calcium flux in {beta}-cells and in their capacity to adapt to metabolic stress.

cell biology↗