Biology subjects

Darabedian, N.

Publications and source records attributed to Darabedian, N..

3 recordsLinked to original sources

bioRxiv2024

A comprehensive landscape of the zinc-regulated human proteome

Zinc is an essential micronutrient that regulates a wide range of physiological processes, principally through Zn2+ binding to protein cysteine residues. Despite being critical for modulation of protein function, for the vast majority of the human proteome the cysteine sites subject to regulation by Zn2+ binding remain undefined. Here we develop ZnCPT, a comprehensive and quantitative mapping of the zinc-regulated cysteine proteome. We define 4807 zinc-regulated protein cysteines, uncovering protein families across major domains of biology that are subject to either constitutive or inducible modification by zinc. ZnCPT enables systematic discovery of zinc-regulated structural, enzymatic, and allosteric functional domains. On this basis, we identify 52 cancer genetic dependencies subject to zinc regulation, and nominate malignancies sensitive to zinc-induced cytotoxicity. In doing so, we discover a mechanism of zinc regulation over Glutathione Reductase (GSR) that drives cell death in GSR-dependent lung cancers. We provide ZnCPT as a resource for understanding mechanisms of zinc regulation over protein function.

cell biology↗

bioRxiv2021

Exo-enzymatic addition of diazirine-modified sialic acid to cell surfaces enables photocrosslinking of glycoproteins

Glycan binding often mediates extracellular macromolecular recognition events. Accurate characterization of these binding interactions can be difficult because of dissociation and scrambling that occur during purification and analysis steps. Use of photocrosslinking methods has been pursued to covalently capture glycan-dependent interactions in situ however use of metabolic glycan engineering methods to incorporate photocrosslinking sugar analogs is limited to certain cell types. Here we report an exo-enzymatic labeling method to add a diazirine-modified sialic acid (SiaDAz) to cell surface glycoconjugates. The method involves chemoenzymatic synthesis of diazirine-modified CMP-sialic acid (CMP-SiaDAz), followed by sialyltransferase-catalyzed addition of SiaDAz to desialylated cell surfaces. Cell surface SiaDAz-ylation is compatible with multiple cell types and is facilitated by endogenous extracellular sialyltransferase activity present in Daudi B cells. This method for extracellular addition of 2-6-linked SiaDAz enables UV-induced crosslinking of CD22, demonstrating the utility for covalent capture of glycan-mediated binding interactions.

biochemistry↗

bioRxiv2019

MYPT1 O-GlcNAcylation controls the sensitivity of fibroblasts to sphingosine-1-phosphate mediated cellular contraction

Many intracellular proteins can be modified by N-acetylglucosamine, a posttranslational modification known as O-GlcNAc. Because this modification is found on serine and threonine side-chains, O-GlcNAc has the potential to dynamically regulate cellular signaling pathways through interplay with phosphorylation. Here, we discover and characterize one such example. First, we find that O-GlcNAc levels control the sensitivity of fibroblasts to actin contraction induced by the signaling lipid sphingosine-1-phosphate (S1P). In follow-up mechanistic investigations, we show that this O-GlcNAc dependence lies in the signaling pathway through the S1PR2 receptor and subsequent activation of the Rho and Rho kinase. This pathway typically culminates in the phosphorylation of myosin light chain (MLC), resulting in myosin activation and cellular contraction. We discovered that O-GlcNAc modification of the phosphatase subunit MYPT1 inhibits this pathway by blocking MYPT1 phosphorylation, maintaining its activity and causing the dephosphorylation of MLC. Therefore, MYTP1 O-GlcNAc levels function to regulate the sensitivity of cells to S1P-mediated cellular contraction. Finally, we demonstrate that O-GlcNAc levels alter the sensitivity of primary human dermal fibroblasts in a collagen matrix model of wound healing. Our findings have important implications for the role of O-GlcNAc in fibroblast motility and differentiation, particularly in diabetic wound healing, where increased levels of the modification may inhibit S1P-mediated healing phenotypes in fibroblasts.

cell biology↗