How SARS-CoV-2 Evades And Suppresses The Immune System (Part 9)

Innate immunity not only acts within cells to suppress microbial invasion and signal nearby cells to impending danger, but also initiates the adaptive immune response. To execute this task, the signaling proteins responsible must exit the cell by traversing the cell membrane.

The principal pathway for signaling protein exit is via interaction with a signal peptide sequence located at the amino terminus of the protein. The signal recognition particle contains both proteins and RNA. The signal peptide sequence ferries signaling proteins to a port on the endoplasmic reticulum. It binds to the first peptides, transports them to the membrane, and from there extrudes them into the lumen, eventually allowing the protein to leave the cell when the endoplasmic reticulum fuses with the membrane.

Almost all proteins that exit the cell, including interferons and other signaling molecules induced by interferons, must follow this pathway. Anything that blocks the pathway will prevent signals from the infected cell from exiting to alert nearby cells or activate other components of the immune system.

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Originally published on Forbes (August 30, 2021)

© William A. Haseltine, PhD. All Rights Reserved.