One can take two very different angles when approaching Bill Kaiserâ€™s and Ed Mocarskiâ€™s work on RIP kinases and the mechanisms of cell death. These are: the evolutionary where-does-apoptosis-come-from angle, and the anti-inflammatory drug discovery angle.
A pair of papers published this week, one in PNAS and one in Journal of Immunology, cover both of these angles. (Also, back to back papers in Cell this week, originating from Australia and Tennessee, touch on the same topic.)
First, the evolutionary angle.
Cellular suicide can be a â€œscorched earthâ€ defense mechanism against viruses. Kaiser and Mocarski have been amassing evidence that some forms of cellular suicide arose as a result of an arms race of competition with viruses. The PNAS paper is part of this line of evidence. It shows that the cell-death circuits controlled by three different genes (RIP1, RIP3 and caspase 8) apparently can be lifted cleanly out of an animal. Mice lacking all three genes not only can be born, but have well-functioning immune systems.
Apoptosis is thought to be a form of cellular suicide important for the development of all multicellular organisms. Thatâ€™s why, to cell and developmental biologists, it seemed rather shocking that researchers can mutate a group of genes that drive apoptosis and other forms of cellular suicide and have adult animals emerge.
Next, the drug discovery angle.
The J. Immunol paper makes that angle clear enough. Most of the authors on this paper are from GlaxoSmithKlineâ€™s â€œPattern Recognition Receptor Discovery Performance Unit, Immuno-Inflammation Therapeutic Area.â€ Here, they show that a mutation in RIP1 inactivating the kinase enzyme protects mice against severe skin and multiorgan inflammation. They conclude their abstract with: “Together, these data suggest that RIP1 kinase represents an attractive therapeutic target for TNF-driven inflammatory diseases.”
Note: TNF-driven inflammatory diseases include rheumatoid arthritis, inflammatory bowel diseases and psoriasis, representing a multibillion dollar market.