Hydrolysis of inositol phospholipids by phospholipase C is initiated by either receptor stimulation or opening of Ca2+ channels. This was once thought to be the sole mechanism to produce the diacylglycerol that links extracellular signals to intracellular events through activation of protein kinase C. It is becoming clear that agonist-induced hydrolysis of other membrane phospholipids, particularly choline phospholipids, by phospholipase D and phospholipase A2 may also take part in cell signaling. The products of hydrolysis of these phospholipids may enhance and prolong the activation of protein kinase C. Such prolonged activation of protein kinase C is essential for long-term cellular responses such as cell proliferation and differentiation.

https://science.sciencemag.org/content/sci/258/5082/607.full.pdf

Intracellular signaling by hydrolysis of phospholipids and activation of protein kinase C

It is increasingly apparent that not only is a cure for the current worldwide diabetes epidemic required, but also for its major complications, affecting both small and large blood vessels. These complications occur in the majority of individuals with both type 1 and type 2 diabetes. Among the most prevalent microvascular complications are kidney disease, blindness, and amputations, with current therapies only slowing disease progression. Impaired kidney function, exhibited as a reduced glomerular filtration rate, is also a major risk factor for macrovascular complications, such as heart attacks and strokes. There have been a large number of new therapies tested in clinical trials for diabetic complications, with, in general, rather disappointing results. Indeed, it remains to be fully defined as to which pathways in diabetic complications are essentially protective rather than pathological, in terms of their effects on the underlying disease process. Furthermore, seemingly independent pathways are also showing significant interactions with each other to exacerbate pathology. Interestingly, some of these pathways may not only play key roles in complications but also in the development of diabetes per se. This review aims to comprehensively discuss the well validated, as well as putative mechanisms involved in the development of diabetic complications. In addition, new fields of research, which warrant further investigation as potential therapeutic targets of the future, will be highlighted.

Mechanisms of Diabetic Complications

cPLA2 is phosphorylated and activated by MAP kinase.

A novel arachidonic acid-selective cytosolic PLA2 contains a Ca2+-dependent translocation domain with homology to PKC and GAP

▪ Abstract Four members of the tumor necrosis factor (TNF) ligand family, TNF-α, LT-α, LT-β, and LIGHT, interact with four receptors of the TNF/nerve growth factor family, the p55 TNF receptor (CD120a), the p75 TNF receptor (CD120b), the lymphotoxin beta receptor (LTβR), and herpes virus entry mediator (HVEM) to control a wide range of innate and adaptive immune response functions. Of these, the most thoroughly studied are cell death induction and regulation of the inflammatory process. Fas/Apo1 (CD95), a receptor of the TNF receptor family activated by a distinct ligand, induces death in cells through mechanisms shared with CD120a. The last four years have seen a proliferation in knowledge of the proteins participating in the signaling by the TNF system and CD95. The downstream signaling molecules identified so far—caspases, phospholipases, the three known mitogen activated protein (MAP) kinase pathways, and the NF-κB activation cascade—mediate the effects of other inducers as well. However, the molecule...

TUMOR NECROSIS FACTOR RECEPTOR AND Fas SIGNALING MECHANISMS

Interleukin 1 and tumor necrosis factor synergistically stimulate prostaglandin synthesis and phospholipase A2 release from rat renal mesangial cells.

Duramycins B and C, two new lanthionine containing antibiotics, have been isolated from Streptoverticillium strain R2075 and Streptomyces griseoluteus (R2107). The known antibiotics duramycin and cinnamycin were reisolated from Streptoverticillium hachijoense (DSM 40114) and Streptomyces longisporoflavus (DSM 40165). The structures of these latter two compounds should be revised by changing ammo acid residue 3 to glutamine and 17 to asparagine, respectively. Cinnamycin therefore seems to be identical to Ro 09-0198. Leucopeptin has been shown to be identical to duramycin. Physico-chemical data of these compounds provide evidence for a similar structure for all duramycin antibiotics. All compounds of this group inhibit human phospholipase A2 at a concentration of 10-6 molar.

Fritz Märki

Papers

Interleukin 1 and tumor necrosis factor synergistically stimulate prostaglandin synthesis and phospholipase A2 release from rat renal mesangial cells.

Duramycins B and C, two new lanthionine containing antibiotics as inhibitors of phospholipase A2. Structural revision of duramycin and cinnamycin.

Interleukin-1β, tumor necrosis factor and forskolin stimulate the synthesis and secretion of group II phospholipase A2 in rat mesangial cells

Endogenous suppression of neutral-active and calcium-dependent phospholipase A2 in human polymorphonuclear leukocytes.

Studies on the acyl-chain selectivity of cellular phospholipases A2