Anexelekto (AXL) no more: microRNA-155 (miR-155) controls the "Uncontrolled" in SARS-CoV-2.

AXL is the gene that encodes the Anexelekto (AXL) receptor tyrosine kinase that demonstrates significant roles in various cellular processes, including cell growth, survival, and migration. Anexelekto is a Greek word meaning excessive and uncontrolled, semantically implying the crucial involvement of AXL in cancer and immune biology, and in promoting cancer metastasis. AXL overexpression appears to drive epithelial to mesenchymal transition, tumor angiogenesis, decreased antitumor immune response, and resistance to therapeutic agents. Recently, AXL has been reported to play important roles in several viral infections, including SARS-CoV-2. We have previously outlined the importance of microRNAs (miRNAs, miRs) and especially miR-155 in SARS-CoV-2 pathophysiology through regulation of the Renin-Angiotensin Aldosterone System (RAAS) and influence on several aspects of host innate immunity. MiRNAs are negative regulators of gene expression, decreasing the stability of target RNAs or limiting their translation and, enthrallingly, miR-155 is also involved in AXL homeostasis-both endogenously and pharmaceutically using repurposed drugs (e.g., metformin)-highlighting thrifty evolutionary host innate immunity mechanisms that successfully can thwart viral entry and replication. Cancer, infections, and immune system disturbances will increasingly involve miRNA diagnostics and therapeutics in the future.