Endoplasmic reticuliun

IPS diffuses to specialized regions of the endoplasmic reticuliun and induces it to release a small amoimt of stored Ca " (Golovina and Blaustein, 1997). The consequent increase in cytoplasmic Ca " levels stimulates a number of events in the cytoplasm, including the further activation of protein kinase C. Calcium ions directly bind to and activate calmodulin, protein kinase C, phospholipase A2, proteins of muscle fibers (troponin, caldesmon), and proteins of the cytoskeleton (gelsolin, villin). One might hesitate to call these proteins Ca-metalloenzymes. It is more accurate to say that these enzymes are regulated by calcium. 

Krishnan N, Fu C, Pappin DJ et al (2011) H2S-lnduced sulfliydration of the phosphatase PTPIB and its role in the endoplasmic reticuliun stress response. Sci Signal 4 ra86... 

WUczynska, Z., Happle, K., MiiUer-Tauben-berger, A., Schlatterer, C., Malchow, D., and Fisher, P. R. (2005) Release of Ca from the endoplasmic reticuliun contributes to Ca signalling in Dictyostelium. Eukaryotic Cell 4, 1513-1525. 

Hence, activation precedes hydroxylation. Although 3-MBFA can be activated at different cellular sites— mitochoniia, peroxisomes and endoplasmic reticuliun —only the peroxisomal activity seems to supply a precursor for the hydroxylation reaction. Whether the acyl-CoA synthetase acting on phytanic acid is the same as the one activating palmitic acid and pristanic acid is a matter of controversy. Anyway, the requirement for an activation step e q)lains the inhibition of a-oxidation by fenoprofen, an inhibitor of long chain fatty acid activation, and by different fatty acids (unpublished data), presumably due to competitive inhibition or by depletion of the available CoA. 

The incorporation of L-[guanido- C]arginine into membranes of the rough and smooth endoplasmic reticuliun in post-ischaemic rat liver showed a lag phase of about 2 h, and was then normally resumed in reversibly injured liver cells (Ferrero et al. 1980). 

Poustka, F., Irani, N.G., FeUer, A. et al. (2007). A trafficking pathway for anthocyanins overlaps with the endoplasmic reticuliun-to-vacuole protein-sorting route in Arabidopsis and contributes to the formation of vacuolar inclusions. Plant Physiology, 145, 1323-1335. 

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