Biology subjects

Azizi, S.-A.

Publications and source records attributed to Azizi, S.-A..

3 recordsLinked to original sources

bioRxiv2021

Regulation of ERK2 activity by dynamic S-acylation

The extracellular signal-regulated kinases (ERK1/2) are key effector proteins of the mitogen-activated protein kinase pathway, choreographing essential processes of cellular physiology. Critical in regulating these regulators are a patchwork of mechanisms, including post-translational modifications (PTMs) such as MEK-mediated phosphorylation. Here, we discover that ERK1/2 are subject to S-palmitoylation, a reversible lipid modification of cysteine residues, at C271/C254. Moreover, the levels of ERK1/2 S-acylation are modulated by epidermal growth factor (EGF) signaling, mirroring its phosphorylation dynamics, and palmitoylation-deficient ERK2 displays altered phosphorylation patterns at key sites. We find that chemical inhibition of either lipid addition or removal significantly alters ERK1/2s EGF-triggered transcriptional program. We also identify a subset of "writer" protein acyl transferases (PATs) and an "eraser" acyl protein thioesterase (APT) that drive ERK1/2s cycle of palmitoylation and depalmitoylation. Finally, we examine ERK1/2 S-acylation in a mouse model of metabolic syndrome, correlating changes in its lipidation levels with alterations in writer/eraser expression and solidifying the link between ERK1/2 activity, ERK1/2 lipidation, and organismal health. This study not only presents a previously undescribed mode of ERK1/2 regulation and a node to modulate MAPK pathway signaling in pathophysiological conditions, it also offers insight into the role of dynamic S-palmitoylation in cell signaling more generally.

biochemistry↗

bioRxiv2020

Drug repurposing screen identifies masitinib as a 3CLpro inhibitor that blocks replication of SARS-CoV-2 in vitro

There is an urgent need for anti-viral agents that treat SARS-CoV-2 infection. The shortest path to clinical use is repurposing of drugs that have an established safety profile in humans. Here, we first screened a library of 1,900 clinically safe drugs for inhibiting replication of OC43, a human beta-coronavirus that causes the common-cold and is a relative of SARS-CoV-2, and identified 108 effective drugs. We further evaluated the top 26 hits and determined their ability to inhibit SARS-CoV-2, as well as other pathogenic RNA viruses. 20 of the 26 drugs significantly inhibited SARS-CoV-2 replication in human lung cells (A549 epithelial cell line), with EC50 values ranging from 0.1 to 8 micromolar. We investigated the mechanism of action for these and found that masitinib, a drug originally developed as a tyrosine-kinase inhibitor for cancer treatment, strongly inhibited the activity of the SARS-CoV-2 main protease 3CLpro. X-ray crystallography revealed that masitinib directly binds to the active site of 3CLpro, thereby blocking its enzymatic activity. Mastinib also inhibited the related viral protease of picornaviruses and blocked picornaviruses replication. Thus, our results show that masitinib has broad anti-viral activity against two distinct beta-coronaviruses and multiple picornaviruses that cause human disease and is a strong candidate for clinical trials to treat SARS-CoV-2 infection.

microbiology↗

bioRxiv2020

Structure of papain-like protease from SARS-CoV-2 and its complexes with non-covalent inhibitors

The number of new cases world-wide for the COVID-19 disease is increasing dramatically, while efforts to contain Severe Acute Respiratory Syndrome Coronavirus 2 is producing varied results in different countries. There are three key SARS-CoV-2 enzymes potentially targetable with antivirals: papain-like protease (PLpro), main protease (Mpro), and RNA-dependent RNA polymerase. Of these, PLpro is an especially attractive target because it plays an essential role in several viral replication processes, including cleavage and maturation of viral polyproteins, assembly of the replicase-transcriptase complex (RTC), and disruption of host viral response machinery to facilitate viral proliferation and replication. Moreover, this enzyme is conserved across different coronaviruses and promising inhibitors have already been discovered for its SARS-CoV variant. Here we report a substantive body of structural, biochemical, and virus replication studies that identify several inhibitors of the enzyme from SARS-CoV-2 in both wild-type and mutant forms. These efforts include the first structures of wild-type PLpro, the active site C111S mutant, and their complexes with inhibitors, determined at 1.60-2.70 Angstroms. This collection of structures provides fundamental molecular and mechanistic insight to PLpro, and critically, illustrates details for inhibitors recognition and interactions. All presented compounds inhibit the peptidase activity of PLpro in vitro, and some molecules block SARS-CoV-2 replication in cell culture assays. These collated findings will accelerate further structure-based drug design efforts targeting PLpro, with the ultimate goal of identifying high-affinity inhibitors of clinical value for SARS-CoV-2.

molecular biology↗