Cytosolic regulation

Chen, M.-Y., Long, Y., and Devreotes, P. N. (1997) A novel cytosolic regulator. Pianissimo, is required for chemoattractant receptor and G protein-mediated activation of the 12 transmembrane domain adenylyl... 

D. discoideum cells of the AX3-derived strain WF38 are used that express a green fluorescent protein (GFP) fused to the pleckstrin homology (PH) domain of the cytosolic regulator of adenylyl cyclase (CRAG). Cells are grown in Petri dishes under HL5 nutrient solution. 

Lilly, P.J. and Devreotes, RN. (1994). Identification of CRAC, a cytosolic regulator required for guanine nucleotide stimulation of adenylyl cyclase in Dictyostelium.. ]. Biol. Chem. 269,14123-14129. 

Cytosolic FBPase is part of the elaborate chloroplastic/cytosolic regulation of sucrose synthesis and carbon partitioning in leaves, which in turn determines the availability of fixed C for export (11). Thus, the reduced levels of FBPase activity in SO2 treated material could be an indication of altered flow of fixed C out of the chloroplast. 

PEP carboxylase occurs in yeast, bacteria, and higher plants, but not in animals. The enzyme is specifically inhibited by aspartate, which is produced by transamination of oxaloacetate. Thus, organisms utilizing this enzyme control aspartate production by regulation of PEP carboxylase. Malic enzyme is found in the cytosol or mitochondria of many animal and plant ceils and is an NADPIT-dependent enzyme. 

It may seem surprising that isocitrate dehydrogenase is strongly regulated, because it is not an apparent branch point within the TCA cycle. However, the citrate/isocitrate ratio controls the rate of production of cytosolic acetyl-CoA, because acetyl-CoA in the cytosol is derived from citrate exported from the mitochondrion. (Breakdown of cytosolic citrate produces oxaloacetate and acetyl-CoA, which can be used in a variety of biosynthetic processes.) Thus, isocitrate dehydrogenase activity in the mitochondrion favors catabolic TCA cycle activity over anabolic utilization of acetyl-CoA in the cytosol. 

Taylor CW, Laude AJ (2002) IP3 receptors and their regulation by calmodulin and cytosolic Ca2+. Cell Calcium 32 321-334... 

---