1.1. Summary

Numerous signal transduction processes involve lipids as signaling molecules. Many of these molecules are generated by phospholipases such as phospholipase A2, which releases fatty acids like arachidonic acid, and lysophospholipids. Each of these products is implicated in signal transduction processes, but also serves as a precursor for platelet activating factor or the eicosanoids, a large familiy of mediators that includes the prostaglandins, leukotrienes, and lipoxins. All of these compounds are implicated in a wide variety of inflammatory diseases such as rheumatoid arthritis, sepsis, intestinal bowel disease, asthma as well as playing a role in cancer and premature parturition. Lipid signaling is also key to the development of obesity and the myriad of illnesses associated to it (e.g. diabetes, cardiovascular disease, etc). Other important phospholipases include phospholipase C, which controls the production of inositol-1,4,5-trisphosphate and diacylglycerol. Phospholipase D generates phosphatidic acid which subsequently can be either metabolized by phospholipase A2 generating lysophosphophatidic acid, a potent cellular mitogen, or by phosphatidate phosphohydrolase, yielding diacylglycerol. Sphingomyelinase, a phospholipase C type enzyme, and related enzymes of sphingolipid metabolism are implicated in apoptosis