COVID-19-specific transcriptomic signature detectable in blood across multiple cohorts

The coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is spreading across the world despite vast global vaccination efforts. Consequently, many studies have looked for potential human host factors and immune mechanisms associated with the disease. However, most studies have focused on comparing COVID-19 patients to healthy controls, while fewer have elucidated the specific host factors distinguishing COVID-19 from other infections. To discover genes specifically related to COVID-19, we reanalyzed transcriptome data from nine independent cohort studies, covering multiple infections, including COVID-19, influenza, seasonal coronaviruses, and bacterial pneumonia. The identified COVID-19-specific signature consisted of 149 genes, involving many signals previously associated with the disease, such as induction of a strong immunoglobulin response and hemostasis, as well as dysregulation of cell cycle-related processes. Additionally, potential new gene candidates related to COVID-19 were discovered. To facilitate exploration of the signature with respect to disease severity, disease progression, and different cell types, we also offer an online tool for easy visualization of the selected genes across multiple datasets at both bulk and single-cell levels.

Adenosine inhibits tumor cell invasion via receptor-independent mechanisms

Extracellular adenosine mediates diverse anti-inflammatory, angiogenic, and other signaling effects via binding to adenosine receptors, and it also regulates cell proliferation and death via activation of the intrinsic signaling pathways. Given the emerging role of adenosine and other purines in tumor growth and metastasis, this study evaluated the effects of adenosine on the invasion of metastatic prostate and breast cancer cells. Treatment with low micromolar concentrations of adenosine, but not other nucleosides or adenosine receptor agonists, inhibited subsequent cell invasion and migration through Matrigel- and laminin-coated inserts. These inhibitory effects occurred via intrinsic receptor-independent mechanisms, despite the abundant expression of A2B adenosine receptors (ADORA2B). Extracellular nucleotides and adenosine were shown to be rapidly metabolized on tumor cell surfaces via sequential ecto-5'-nucleotidase (CD73/NT5E) and adenosine deaminase reactions with subsequent cellular uptake of nucleoside metabolites and their intracellular interconversion into ADP/ATP. This was accompanied by concurrent inhibition of AMP-activated protein kinase and other signaling pathways. No differences in the proliferation rates, cytoskeleton assembly, expression of major adhesion molecules [integrin-1β (ITGB1), CD44, focal adhesion kinase], and secretion of matrix metalloproteinases were detected between the control and treated cells, thus excluding the contribution of these components of invasion cascade to the inhibitory effects of adenosine. These data provide a novel insight into the ability of adenosine to dampen immune responses and prevent tumor invasion via two different, adenosine receptor-dependent and -independent mechanisms.

IMPLICATIONS

This study suggests that the combined targeting of adenosine receptors and modulation of intracellular purine levels can affect tumor growth and metastasis phenotypes.

Loss of p38gamma MAPK induces pleiotropic mitotic defects and massive cell death

The p38 mitogen-activated protein kinase (p38 MAPK) family, which is comprised of four protein isoforms, p38α, p38β, p38γ and p38δ, forms one of the key MAPK pathways. The p38 MAPKs are implicated in many cellular processes including inflammation, differentiation, cell growth, cell cycle and cell death. The function of p38 MAPKs in mitotic entry has been well established, but their role in mitotic progression has remained controversial. We identify p38γ MAPK as a modulator of mitotic progression and mitotic cell death. In HeLa cells, loss of p38γ results in multipolar spindle formation and chromosome misalignment, which induce a transient M phase arrest. The majority of p38γ-depleted cells die at mitotic arrest or soon after abnormal exit from M-phase. We show that p38 MAPKs are activated at the kinetochores and spindle poles throughout mitosis by kinase(s) that are stably bound to these structures. Finally, p38γ is required for the normal kinetochore localization of polo-like kinase 1 (Plk1), and this contributes to the activity of the p38 MAPK pathway. Our data suggest a link between mitotic regulation and the p38 MAPK pathway, in which p38γ prevents chromosomal instability and supports mitotic cell viability.