Cyclic nucleotide-dependent phosphorylation of rat intestinal microvillus and basal-lateral membrane proteins by an endogenous protein kinase.
Both the microvillus and basal-lateral membrane components of intestinal epithelial cells were found to contain endogenous cyclic nucleotide-dependent protein kinases and their endogenous protein substrates. The phosphorylation of either membrane component using [gamma-32P]ATP as substrate, occurred very rapidly, reaching maximal levels at 1 min. Both cyclic AMP and cyclic GMP were shown to stimulate the phosphorylation of the microvillus and basal-lateral membranes; the approximate concentrations of cyclic AMP and cyclic GMP required for half-maximal stimulation of phosphorylation were 2 x 10(-7) M and 1.7 x 10(-8) M, respectively, for the basal-lateral membranes, and 2 x 10(-7) M and 3.2 x 10(-8) M, respectively, for the microvillus membranes. Although both membrane components were phosphorylated by an endogenous protein kinase, the microvillus membrane was consistently phosphorylated to a greater extent at maximally effective concentrations of either cyclic nucleotide. The microvillus and basal-lateral membranes were also found to contain a phosphoprotein phosphatase; however, the rate of removal of [32P]phosphate from the microvillus membrane was found to be more rapid. Neither cyclic AMP nor cyclic GMP altered the activity of the enzyme in either membrane. The present results together with earlier studies are compatible with the possibility that the regulation of water and electrolyte transport in the small intestine by cyclic AMP and cyclic GMP may be mediated through modulation of the phosphorylation of protein components of the microvillus and basal-lateral membranes.
D000251:Adenosine Triphosphatases / Q000032:analysis / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000032:analysis / Q000378:metabolism; D000818:Animals; D000242:Cyclic AMP / Q000008:administration & dosage / Q000494:pharmacology*; D006152:Cyclic GMP / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006162:Guanylate Cyclase / Q000032:analysis / Q000378:metabolism; D007413:Intestinal Mucosa / Q000201:enzymology / Q000378:metabolism*; D007421:Intestine, Small / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D011494:Protein Kinases / Q000032:analysis / Q000502:physiology*; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis / Q000378:metabolism; D013997:Time Factors
D008565:Membrane Proteins; D010761:Phosphorus Radioisotopes; D000242:Cyclic AMP; D011494:Protein Kinases; D010749:Phosphoprotein Phosphatases; D000251:Adenosine Triphosphatases; D000262:Adenylyl Cyclases; D006162:Guanylate Cyclase; D000254:Sodium-Potassium-Exchanging ATPase; D006152:Cyclic GMP