The mechanism of covalent inhibition of LAR phosphatase by illudalic acid.

Leukocyte antigen-related (LAR) phosphatase is a receptor-type protein tyrosine phosphatase involved in cellular signaling and associated with human disease including cancer and metabolic disorders. Selective inhibition of LAR phosphatase activity by well characterized and well validated small molecules would provide key insights into the roles of LAR phosphatase in health and disease, but identifying selective inhibitors of LAR phosphatase activity has been challenging. Recently, we described potent and selective inhibition of LAR phosphatase activity by the fungal natural product illudalic acid. Here we provide a detailed biochemical characterization of the adduct formed between LAR phosphatase and illudalic acid. A mass spectrometric analysis indicates that two cysteine residues are covalently labeled by illudalic acid and a related analog. Mutational analysis supports the hypothesis that inhibition of LAR phosphatase activity is due primarily to the adduct with the catalytic cysteine residue. A computational study suggests potential interactions between the illudalic acid moiety and the enzyme active site. Taken together, these data offer novel insights into the mechanism of inhibition of LAR phosphatase activity by illudalic acid.

Zinc Alpha-2-Glycoprotein (ZAG/AZGP1) secreted by triple-negative breast cancer promotes tumor microenvironment fibrosis.

Obesity is a predisposition factor for breast cancer, suggesting a localized, reciprocal interaction between breast cancer cells and the surrounding mammary white adipose tissue. To investigate how breast cancer cells alter the composition and function of adipose tissue, we screened the secretomes of ten human breast cancer cell lines for the ability to modulate the differentiation of adipocyte stem and progenitor cells (ASPC). The screen identified a key adipogenic modulator, Zinc Alpha-2-Glycoprotein (ZAG/AZGP1), secreted by triple-negative breast cancer (TNBC) cells. TNBC-secreted ZAG inhibits adipogenesis and instead induces the expression of fibrotic genes. Accordingly, depletion of ZAG in TNBC cells attenuates fibrosis in white adipose tissue and inhibits tumor growth. Further, high expression of ZAG in TNBC patients, but not other clinical subtypes of breast cancer, is linked to poor prognosis. Our findings suggest a role of TNBC-secreted ZAG in promoting the transdifferentiation of ASPCs into cancer-associated fibroblasts to support tumorigenesis.

SARS-CoV-2 innate effector associations and viral load in early nasopharyngeal infection.

COVID-19 causes severe disease with poor outcomes. We tested the hypothesis that early SARS-CoV-2 viral infection disrupts innate immune responses. These changes may be important for understanding subsequent clinical outcomes. We obtained residual nasopharyngeal swab samples from individuals who requested COVID-19 testing for symptoms at drive-through COVID-19 clinical testing sites operated by the University of Utah. We applied multiplex immunoassays, real-time polymerase chain reaction assays and quantitative proteomics to 20 virus-positive and 20 virus-negative samples. ACE-2 transcripts increased with infection (OR =17.4, 95% CI [CI] =4.78-63.8) and increasing viral N1 protein transcript load (OR =1.16, CI =1.10-1.23). Transcripts for two interferons (IFN) were elevated, IFN-λ1 (OR =71, CI =7.07-713) and IFN-λ2 (OR =40.2, CI =3.86-419), and closely associated with viral N1 transcripts (OR =1.35, CI =1.23-1.49 and OR =1.33 CI =1.20-1.47, respectively). Only transcripts for IP-10 were increased among systemic inflammatory cytokines that we examined (OR =131, CI =1.01-2620). We found widespread discrepancies between transcription and translation. IFN proteins were unchanged or decreased in infected samples (IFN-γ OR =0.90 CI =0.33-0.79, IFN-λ2,3 OR =0.60 CI =0.48-0.74) suggesting viral-induced shut-off of host antiviral protein responses. However, proteins for IP-10 (OR =3.74 CI =2.07-6.77) and several interferon-stimulated genes (ISG) increased with viral load (BST-1 OR =25.1, CI =3.33-188; IFIT1 OR =19.5, CI =4.25-89.2; IFIT3 OR =245, CI =15-4020; MX-1 OR =3.33, CI =1.44-7.70). Older age was associated with substantial modifications of some effects. Ambulatory symptomatic patients had an innate immune response with SARS-CoV-2 infection characterized by elevated IFN, proinflammatory cytokine and ISG transcripts, but there is evidence of a viral-induced host shut-off of antiviral responses. Our findings may characterize the disrupted immune landscape common in patients with early disease.

SARS-CoV-2 Innate Effector Associations and Viral Load in Early Nasopharyngeal Infection.

To examine innate immune responses in early SARS-CoV-2 infection that may change clinical outcomes, we compared nasopharyngeal swab data from 20 virus-positive and 20 virus-negative individuals. Multiple innate immune-related and ACE-2 transcripts increased with infection and were strongly associated with increasing viral load. We found widespread discrepancies between transcription and translation. Interferon proteins were unchanged or decreased in infected samples suggesting virally-induced shut-off of host anti-viral protein responses. However, IP-10 and several interferon-stimulated gene proteins increased with viral load. Older age was associated with modifications of some effects. Our findings may characterize the disrupted immune landscape of early disease.