Aquaporin-1 Channel Function Is Positively Regulated by Protein Kinase C

Abstract

Aquaporin-1 (AQP1) channels contribute to osmotically induced water transport in several organs including the kidney and serosal membranes such as the peritoneum and the pleura. In addition, AQP1 channels have been shown to conduct cationic currents upon stimulation by cyclic nucleotides. To date, the short term regulation of AQP1 function by other major intracellular signaling pathways has not been studied. In the present study, we therefore investigated the regulation of AQP1 by protein kinase C. AQP1 wild type channels were expressed in Xenopus oocytes. Water permeability was assessed by hypotonic challenges. Activation of protein kinase C (PKC) by 1-oleoyl-2-acetyl-sn-glycerol (OAG) induced a marked increase of AQP1-dependent water permeability. This regulation was abolished in mutated AQP1 channels lacking both consensus PKC phosphorylation sites Thr157 and Thr239 (termed AQP1 ΔPKC). AQP1 cationic currents measured with double-electrode voltage clamp were markedly increased after pharmacological activation of PKC by either OAG or phorbol 12-myristate 13-acetate. Deletion of either Thr157 or Thr239 caused a marked attenuation of PKC-dependent current increases, and deletion of both phosphorylation sites in AQP1 ΔPKC channels abolished the effect. In vitro phosphorylation studies with synthesized peptides corresponding to amino acids 154–168 and 236–250 revealed that both Thr157 and Thr239 are phosphorylated by PKC. Upon stimulation by cyclic nucleotides, AQP1 wild type currents exhibited a strong activation. This regulation was not affected after deletion of PKC phosphorylation sites in AQP1 ΔPKC channels. In conclusion, this is the first study to show that PKC positively regulates both water permeability and ionic conductance of AQP1 channels. This new pathway of AQP1 regulation is independent of the previously described cyclic nucleotide pathway and may contribute to the PKC stimulation of AQP1-modulated processes such as endothelial permeability, angiogenesis, and urine concentration. Aquaporin-1 (AQP1) channels contribute to osmotically induced water transport in several organs including the kidney and serosal membranes such as the peritoneum and the pleura. In addition, AQP1 channels have been shown to conduct cationic currents upon stimulation by cyclic nucleotides. To date, the short term regulation of AQP1 function by other major intracellular signaling pathways has not been studied. In the present study, we therefore investigated the regulation of AQP1 by protein kinase C. AQP1 wild type channels were expressed in Xenopus oocytes. Water permeability was assessed by hypotonic challenges. Activation of protein kinase C (PKC) by 1-oleoyl-2-acetyl-sn-glycerol (OAG) induced a marked increase of AQP1-dependent water permeability. This regulation was abolished in mutated AQP1 channels lacking both consensus PKC phosphorylation sites Thr157 and Thr239 (termed AQP1 ΔPKC). AQP1 cationic currents measured with double-electrode voltage clamp were markedly increased after pharmacological activation of PKC by either OAG or phorbol 12-myristate 13-acetate. Deletion of either Thr157 or Thr239 caused a marked attenuation of PKC-dependent current increases, and deletion of both phosphorylation sites in AQP1 ΔPKC channels abolished the effect. In vitro phosphorylation studies with synthesized peptides corresponding to amino acids 154–168 and 236–250 revealed that both Thr157 and Thr239 are phosphorylated by PKC. Upon stimulation by cyclic nucleotides, AQP1 wild type currents exhibited a strong activation. This regulation was not affected after deletion of PKC phosphorylation sites in AQP1 ΔPKC channels. In conclusion, this is the first study to show that PKC positively regulates both water permeability and ionic conductance of AQP1 channels. This new pathway of AQP1 regulation is independent of the previously described cyclic nucleotide pathway and may contribute to the PKC stimulation of AQP1-modulated processes such as endothelial permeability, angiogenesis, and urine concentration. The aquaporins (AQPs) 3The abbreviations used are: AQP, aquaporin; PKC, protein kinase C; OAG, 1-oleoyl-2-acetyl-sn-glycerol; PMA, phorbol 12-myristate 13-acetate; MOPS, 4-morpholinepropanesulfonic acid; IBMX, isobutylmethylxanthine; CN, cyclic nucleotide; ODQ, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one. 3The abbreviations used are: AQP, aquaporin; PKC, protein kinase C; OAG, 1-oleoyl-2-acetyl-sn-glycerol; PMA, phorbol 12-myristate 13-acetate; MOPS, 4-morpholinepropanesulfonic acid; IBMX, isobutylmethylxanthine; CN, cyclic nucleotide; ODQ, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one. are a family of integral membrane proteins that are widely expressed in bacteria, plants, and animals (1Agre P. King L.S. Yasui M. Guggino W.B. Ottersen O.P. Fujiyoshi Y. Engel A. Nielsen S. J. Physiol. 2002; 542: 3-16Crossref PubMed Scopus (891) Google Scholar). Their main physiological function is rapid transmembrane transport of water driven by osmotic gradients. In addition to water transport, some aquaporins also conduct ion currents. In humans, 11 aquaporins have been found so far (AQP0–AQP10). Of these, AQP1 is the predominant and least specialized subtype. It plays a major role in constitutive water transport through the membranes of several cell types including endothelial cells, red blood cells, and renal proximal tubule cells (1Agre P. King L.S. Yasui M. Guggino W.B. Ottersen O.P. Fujiyoshi Y. Engel A. Nielsen S. J. Physiol. 2002; 542: 3-16Crossref PubMed Scopus (891) Google Scholar). It has been shown that AQP1 may also function as a cyclic nucleotide-gated cation channel that is activated mainly by cGMP and indirectly also by cAMP (2Anthony T.L. Brooks H.L. Boassa D. Leonov S. Yanochko G.M. Regan J.W. Yool A.W. Mol. Pharmacol. 2000; 57: 576-588Crossref PubMed Scopus (144) Google Scholar, 3Yool A.J. Stamer D. Regan J.W. Science. 1996; 273: 1216-1218Crossref PubMed Scopus (141) Google Scholar). Recently, ion currents of native aquaporins were confirmed in choroid plexus epithelium and shown to modulate fluid transport of those cells (4Boassa D. Stamer W.D. Yool A.J. J. Neurosci. 2006; 26: 7811-7819Crossref PubMed Scopus (79) Google Scholar). Because of its significance for determining endothelial water permeability, AQP1 has been found to play a major physiological role in the peritoneal membrane (5Devuyst O. Ni J. Verbavatz J. Biol. Cell. 2005; 97: 667-673Crossref PubMed Scopus (18) Google Scholar). Subsequently, it has been shown to be the molecular correlate of the “ultrasmall pore” responsible for transcellular water permeability during peritoneal dialysis (6Ni J. Verbavatz J.M. Rippe A. Boisde I. Moulin P. Rippe B. Verkman A.S. Devuyst O. Kidney Int. 2006; 69: 1518-1525Abstract Full Text Full Text PDF PubMed Scopus (125) Google Scholar). Furthermore, recent reports have demonstrated a previously unexpected role of AQP1 in cell migration (7Sadoun S. Papadopoulos M.C. Hara-Chikuma M. Verkman A.S. Nature. 2005; 434: 786-791Crossref PubMed Scopus (632) Google Scholar, 8Hara-Chikuma M. Verkman A.S. J. Am. Soc. Nephrol. 2006; 17: 39-45Crossref PubMed Scopus (142) Google Scholar, 9Belge H. Devuyst O. Nephrol. Dial. Transplant. 2006; 21: 2069-2071Crossref PubMed Scopus (10) Google Scholar). Endothelial cells lacking AQP1 have impaired cell motility because of reduced formation of lamellipodia, resulting in impaired angiogenesis (7Sadoun S. Papadopoulos M.C. Hara-Chikuma M. Verkman A.S. Nature. 2005; 434: 786-791Crossref PubMed Scopus (632) Google Scholar). Interestingly, AQP1 was also found to be essential for normal migration of renal proximal tubule cells and restitution of renal injury (8Hara-Chikuma M. Verkman A.S. J. Am. Soc. Nephrol. 2006; 17: 39-45Crossref PubMed Scopus (142) Google Scholar, 9Belge H. Devuyst O. Nephrol. Dial. Transplant. 2006; 21: 2069-2071Crossref PubMed Scopus (10) Google Scholar). It is well documented that aquaporin channels may be subject to intense short term regulation by cellular signal cascades, with the most recognized example being the cAMP-dependent protein kinase-dependent regulation of AQP-2 in the kidney collecting duct (1Agre P. King L.S. Yasui M. Guggino W.B. Ottersen O.P. Fujiyoshi Y. Engel A. Nielsen S. J. Physiol. 2002; 542: 3-16Crossref PubMed Scopus (891) Google Scholar, 10Verkman A.S. J. Cell Sci. 2002; 118: 3225-3232Crossref Scopus (481) Google Scholar). Interestingly, however, little is known to date about the short term regulation of AQP1, because this channel was originally considered to be constitutively open (1Agre P. King L.S. Yasui M. Guggino W.B. Ottersen O.P. Fujiyoshi Y. Engel A. Nielsen S. J. Physiol. 2002; 542: 3-16Crossref PubMed Scopus (891) Google Scholar). The role of signaling pathways apart from cyclic nucleotides in the regulation of AQP1 has not been investigated to date. The protein kinase C (PKC) system is a key component of intracellular signaling, and PKC activation is a central pathway downstream of Gq/11 coupled receptors such as adrenergic α1 receptors and muscarinergic M1 receptors (11Rockman H.A. Koch W.J. Lefkowitz R.J. Nature. 2002; 415: 206-212Crossref PubMed Scopus (771) Google Scholar, 12Nishizuka Y. FASEB J. 1995; 9: 484-496Crossref PubMed Scopus (2347) Google Scholar). PKC has been shown to be involved in the regulation of structurally diverse membrane proteins, particularly ion channels (13Karle C.A. Zitron E. Zhang W. Wendt-Nordahl G. Kathoöfer S. Thomas D. Gut B. E. H.A. J. 2002; PubMed Scopus Google Scholar, C. Zitron E. D. S. M. S. Thomas D. J. H.A. W. C.A. J. Mol. 2006; PubMed Scopus Google Scholar). Recently, it has been demonstrated that PKC the of renal channels M. S. H. A. Am. J. Physiol. 2002; PubMed Scopus Google Scholar, J. Biol. 273: Full Text Full Text PDF PubMed Scopus Google Scholar). a major role of PKC in the regulation of endothelial permeability, angiogenesis, and water transport in the proximal renal tubule has been in physiological studies J. S. J.M. 2000; PubMed Scopus Google Scholar, A. A. Am. J. Physiol. PubMed Scopus Google Scholar, Pharmacol. Physiol. 2005; PubMed Scopus Google Scholar, J. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar, A. M. S. 2002; PubMed Scopus Google Scholar, M. and Scholar, M. Am. J. Physiol. PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar). we show that PKC positively regulates AQP1 channels expressed in Xenopus oocytes. PKC activation increase of both water permeability and ion currents by the molecular the both consensus PKC phosphorylation sites Thr157 and Thr239 with of the being to and voltage clamp of Xenopus were in and was from the to currents in the as described by J. Physiol. PubMed Scopus Google Scholar). and voltage were with OAG and from were in to of and of the were to the with the the of The of in the the measured currents. of the were and voltage clamp was used to currents from Xenopus as previously (13Karle C.A. Zitron E. Zhang W. Wendt-Nordahl G. Kathoöfer S. Thomas D. Gut B. E. H.A. J. 2002; PubMed Scopus Google Scholar). was used for of the voltage and for The are as the significance was for and of for of several of The were considered to be the was and the was In the significance are by of the were in from least of permeability were with the of or from with water as described by (2Anthony T.L. Brooks H.L. Boassa D. Leonov S. Yanochko G.M. Regan J.W. Yool A.W. Mol. Pharmacol. 2000; 57: 576-588Crossref PubMed Scopus (144) Google Scholar). the of the the were of for were with the of with a a The were as in and to the of the were in from least revealed PKC phosphorylation Thr157 and To phosphorylation the were with This in the mutated channels and both were a were with the used the and to and for we used the and of the used in this study were by of AQP1 in Xenopus AQP1 wild type was a from was from the corresponding and with after with the in vitro AQP1 of wild type and channels the of was and a The of was The were after corresponding to amino 154–168 with a of by to and to 236–250 with a of by to were from peptides and were from the and to as and In of and of PKC Cell were for in the of was of MOPS, of and of including and in The were by and the was for The peptides were by The were and to The were with the of and and Xenopus were used to membrane were in of hypotonic a for of the were The were and to the oocytes. The and cellular were for The membranes were for The membrane were in of protein for and a were The were for with The were with AQP1 in The were for with and with for and were were C Activation Water of Aquaporin-1 AQP1 channels were expressed in Xenopus to of water permeability and ion water permeability of the membrane of those cells was assessed by hypotonic to (2Anthony T.L. Brooks H.L. Boassa D. Leonov S. Yanochko G.M. Regan J.W. Yool A.W. Mol. Pharmacol. 2000; 57: 576-588Crossref PubMed Scopus (144) Google Scholar). The of to be to in other studies (2Anthony T.L. Brooks H.L. Boassa D. Leonov S. Yanochko G.M. Regan J.W. Yool A.W. Mol. Pharmacol. 2000; 57: 576-588Crossref PubMed Scopus (144) Google to cell as a of the To PKC in a of PKC OAG and of the physiological was to the a of of cells in OAG was of the of in those cells is in cell increased to in with addition of OAG to the cells AQP1 exhibited a increase to from the of OAG with that not AQP1 not show in with cells of Aquaporin-1 Water by PKC in Thr157 and of AQP1 channel amino revealed consensus sites for PKC phosphorylation Thr157 and To the role of those we channel by The was by to phosphorylation the lacking both PKC phosphorylation sites including and were and measured to those described for wild type channels. The are in of to the the of channels increased to of the were and OAG was to the to PKC. In to the in AQP1 increase was not by PKC activation in channels. the of the of those cells increased to to those of OAG we that of both PKC phosphorylation sites the regulation of AQP1 water permeability by protein kinase C. C Activation Aquaporin-1 has been demonstrated previously that AQP1 channels also conduct and that this conductance is activated by increase in intracellular cyclic nucleotide particularly cGMP and also cAMP (2Anthony T.L. Brooks H.L. Boassa D. Leonov S. Yanochko G.M. Regan J.W. Yool A.W. Mol. Pharmacol. 2000; 57: 576-588Crossref PubMed Scopus (144) Google Scholar, 3Yool A.J. Stamer D. Regan J.W. Science. 1996; 273: 1216-1218Crossref PubMed Scopus (141) Google Scholar). we the PKC system also regulates AQP1 ion currents. voltage was used to AQP1 currents in Xenopus channels. a of that is to the of AQP1 currents in voltage to from to were a phorbol was the for to PKC. In to the water permeability the not the of the cells and therefore be to of of that a of the were of the of the current during the to were and with and after of to are shown in the cells exhibited currents with a of and of or of induced a marked increase of currents and of the the currents increased and a after a increase of current by was in with were with that not cells exhibited a current increase and AQP1 were for the addition of to the a current increase was in those cells and is a well and of PKC, it is we the OAG of to the role of PKC in the effect. Because OAG is PMA, a of OAG to be as used in studies from (13Karle C.A. Zitron E. Zhang W. Wendt-Nordahl G. Kathoöfer S. Thomas D. Gut B. E. H.A. J. 2002; PubMed Scopus Google Scholar). The were as described for The are shown in OAG also induced a marked current increase current of was with that with currents increased by in with of PKC the resulting in a current increase by and either to OAG or of AQP1 current of and and The current in of the described in this study were and of significance with the Their was the of current that are in the Xenopus system E. C. S. Kathoöfer S. Thomas D. J. H.A. W. C.A. PubMed Scopus Google Scholar, E. S. C. Thomas D. S. J. H.A. W. C.A. 2005; PubMed Scopus Google Scholar, J. Pharmacol. 2002; PubMed Scopus Google Scholar). of corresponding are shown in with the and and and and and sites Thr157 and Thr239 are essential for protein kinase C regulation of channels. Aquaporin-1 channels PKC phosphorylation sites Thr157 and AQP1 channels with and or with both sites were measured to those described for AQP1 channels. PKC was activated by of OAG currents were with those of AQP1 and exhibited the of cells AQP1 and channels demonstrated in with those from the (2Anthony T.L. Brooks H.L. Boassa D. Leonov S. Yanochko G.M. Regan J.W. Yool A.W. Mol. Pharmacol. 2000; 57: 576-588Crossref PubMed Scopus (144) Google Scholar, 3Yool A.J. Stamer D. Regan J.W. Science. 1996; 273: 1216-1218Crossref PubMed Scopus (141) Google as in in The of the is marked by the and the the of the were used as however, AQP1 exhibited a markedly to OAG of is in D. the in wild type channels is after are shown in E. of either of the sites reduced PKC to of the in wild type channels with in and in In channels lacking both the was with those of the with and with with the with wild type channels and with those with that not In of the in vitro phosphorylation of peptides to the phosphorylation sites and the are The is shown in the were in The of the corresponding is shown as type peptides and were subject to intense phosphorylation in the corresponding peptides and were not phosphorylated from to in nucleotide induced activation of AQP1 conductance is independent of the protein kinase C It has been demonstrated previously that ionic conductance of AQP1 channels is positively by cyclic nucleotides, mainly cGMP and cAMP (2Anthony T.L. Brooks H.L. Boassa D. Leonov S. Yanochko G.M. Regan J.W. Yool A.W. Mol. Pharmacol. 2000; 57: 576-588Crossref PubMed Scopus (144) Google Scholar, 3Yool A.J. Stamer D. Regan J.W. Science. 1996; 273: 1216-1218Crossref PubMed Scopus (141) Google Scholar). To this pathway is in channels lacking PKC phosphorylation intracellular of cyclic nucleotides were increased by of and to the shown in this induced a marked current increase after the of In with AQP1 currents also increased markedly upon to and The of is in D. The are shown in and induced strong current in AQP1 channels and in channels This be by of In of and IBMX, currents increased to and with cells that not AQP1 either in AQP1 and in channels were that cyclic activation of AQP1 is independent of the protein kinase C from to in Thr157 and Thr239 for C of Aquaporin-1 that PKC regulation of AQP1 water permeability was found to the of phosphorylation sites Thr157 and we investigated the role of for the current channels and both in were measured to those described for wild type channels. OAG was used to PKC. In of currents and after to OAG are current were from the wild in to wild type channels not the strong activation induced by was a current increase by and the was in wild type channels The channels in of the PKC phosphorylation sites been and activation by OAG and in with wild current were in and in in those channels were and wild type and that of the PKC-dependent may be to of the with and channels of OAG a current increase with that of AQP1 wild type channels and was with AQP1 wild type and channels. In membranes from the of were found the with in wild type and channels were used as To phosphorylation of the consensus sites that were found to be essential for the regulation of AQP1 by PKC in the we in vitro peptides were synthesized corresponding to the wild type amino those and In those peptides were phosphorylated by PKC peptides were synthesized that the corresponding of the channels and The resulting peptides to as and were for phosphorylation In to the wild type PKC phosphorylation was in the peptides Activation of AQP1 of the C has been shown previously that both AQP1 ion conductance and water permeability may be positively by cyclic nucleotides (2Anthony T.L. Brooks H.L. Boassa D. Leonov S. Yanochko G.M. Regan J.W. Yool A.W. Mol. Pharmacol. 2000; 57: 576-588Crossref PubMed Scopus (144) Google Scholar, 3Yool A.J. Stamer D. Regan J.W. Science. 1996; 273: 1216-1218Crossref PubMed Scopus (141) Google Scholar). demonstrated that protein kinase C also regulates AQP1 we were in is those signaling channels lacking PKC phosphorylation sites were expressed in Xenopus and and were to increase intracellular cyclic nucleotide were with the as used for the PKC with the voltage and the The are shown in In AQP1 wild type of and induced a strong increase of currents by with after and channels exhibited a with a current increase by with and of the resulting in a current increase by and that for a predominant role of cGMP in with from other (2Anthony T.L. Brooks H.L. Boassa D. Leonov S. Yanochko G.M. Regan J.W. Yool A.W. Mol. Pharmacol. 2000; 57: 576-588Crossref PubMed Scopus (144) Google Scholar, D. Stamer W.D. Yool A.J. J. Neurosci. 2006; 26: 7811-7819Crossref PubMed Scopus (79) Google Scholar). were with cells that not AQP1 channels or with with the and IBMX, In those current the of the current were and we were to the previously described regulation of AQP1 conductance by cyclic nucleotides in wild type channels with a predominant role of Interestingly, mutated AQP1 channels lacking PKC phosphorylation sites exhibited a to this that both pathways AQP1 channels. To the of this is the first study to show that protein kinase C positively regulates channels. Furthermore, we that this new pathway of AQP1 regulation is independent of the previously described cyclic nucleotide of AQP1 by of protein kinase C ion currents and water permeability by channels was in this it is not to both of AQP1 function Furthermore, of water permeability are by the of the cells that not Because the of ion currents the voltage clamp were used for and for a of the molecular of are that protein kinase C regulates channel PKC OAG and induced increase of AQP1 function with a that is for kinase-dependent regulation in this system (13Karle C.A. Zitron E. Zhang W. Wendt-Nordahl G. Kathoöfer S. Thomas D. Gut B. E. H.A. J. 2002; PubMed Scopus Google Scholar, C. Zitron E. D. S. M. S. Thomas D. J. H.A. W. C.A. J. Mol. 2006; PubMed Scopus Google Scholar, E. C. S. Kathoöfer S. Thomas D. J. H.A. W. C.A. PubMed Scopus Google Scholar). This not water channels or ion channels of Xenopus because it was not in oocytes. the be by of PKC of the PKC consensus sites of AQP1 abolished the Interestingly, of either of the consensus sites the regulation to a current increase that was in the in the in wild type channels and in AQP1 ΔPKC channels. the of the phosphorylation sites to be independent of other with of the effect. in vitro phosphorylation synthesized peptides demonstrated that peptides corresponding to the wild type Thr157 and Thr239 are phosphorylated by PKC, peptides corresponding to the and are with the the phosphorylation for a major role for both PKC phosphorylation sites in the of the AQP1 Activation the PKC and the date, little has been to the short term regulation of cyclic nucleotide signaling pathways have been shown to modulate AQP1 cGMP and also indirectly cAMP increase of water permeability and to cationic currents (2Anthony T.L. Brooks H.L. Boassa D. Leonov S. Yanochko G.M. Regan J.W. Yool A.W. Mol. Pharmacol. 2000; 57: 576-588Crossref PubMed Scopus (144) Google Scholar, 3Yool A.J. Stamer D. Regan J.W. Science. 1996; 273: 1216-1218Crossref PubMed Scopus (141) Google Scholar). This be in AQP1 wild type channels in this the molecular regulation of AQP1 has not been because AQP1 not a and cAMP-dependent protein kinase consensus sites (4Boassa D. Stamer W.D. Yool A.J. J. Neurosci. 2006; 26: 7811-7819Crossref PubMed Scopus (79) Google Scholar, D. Yool A.J. Physiol. PubMed Google Scholar). In this study, we a with protein kinase increase of both water permeability and ionic currents. were therefore in about AQP1 ΔPKC channels with abolished PKC-dependent regulation were to and that increase of intracellular channels exhibited a marked current increase that was to that of AQP1 wild type channels. therefore that those pathways is and that both pathways molecular to AQP1 AQP1 has been as constitutively water permeability (1Agre P. King L.S. Yasui M. Guggino W.B. Ottersen O.P. Fujiyoshi Y. Engel A. Nielsen S. J. Physiol. 2002; 542: 3-16Crossref PubMed Scopus (891) Google Scholar). regulation has mainly been investigated the with for by and by (5Devuyst O. Ni J. Verbavatz J. Biol. Cell. 2005; 97: 667-673Crossref PubMed Scopus (18) Google Scholar). In this study, we have shown a regulation of AQP1 function by the PKC PKC signaling has been in physiological processes that have also been to AQP1 such as endothelial permeability, angiogenesis, and urine J. S. J.M. 2000; PubMed Scopus Google Scholar, A. A. Am. J. Physiol. PubMed Scopus Google Scholar, Pharmacol. Physiol. 2005; PubMed Scopus Google Scholar, J. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar, A. M. S. 2002; PubMed Scopus Google Scholar, M. and Scholar, M. Am. J. Physiol. PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar). PKC angiogenesis, and increased AQP1 function has been shown to be a of endothelial cell migration and angiogenesis (7Sadoun S. Papadopoulos M.C. Hara-Chikuma M. Verkman A.S. Nature. 2005; 434: 786-791Crossref PubMed Scopus (632) Google Scholar, 8Hara-Chikuma M. Verkman A.S. J. Am. Soc. Nephrol. 2006; 17: 39-45Crossref PubMed Scopus (142) Google Scholar, 9Belge H. Devuyst O. Nephrol. Dial. Transplant. 2006; 21: 2069-2071Crossref PubMed Scopus (10) Google Scholar, J. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar, A. M. S. 2002; PubMed Scopus Google Scholar, M. and Scholar). It is well documented that PKC signaling endothelial permeability and urine both of may increase of water J. S. J.M. 2000; PubMed Scopus Google Scholar, A. A. Am. J. Physiol. PubMed Scopus Google Scholar, Pharmacol. Physiol. 2005; PubMed Scopus Google Scholar, J. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar, M. Am. J. Physiol. PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar). it is to that increase of AQP1 function may also contribute to the stimulation of those processes by PKC. AQP1 is of several aquaporins that have been shown to conduct ion currents in addition to water J. Yool A.J. E. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar, A.J. Physiol. Sci. 2002; 17: Google Scholar). the physiological role of those currents has a of because of the of ionic conductance to water S. B. D. W. P. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar, D. P. P. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). It has been that ion may be involved in the of ionic and osmotic of A.J. Physiol. Sci. 2002; 17: Google with the function to channels in M. A. M. P. Ottersen O.P. Sci. S. A. PubMed Scopus Google Scholar). Recently, a function of AQP1 water and ion transport has been shown in choroid plexus for the first a physiological function of currents in native (4Boassa D. Stamer W.D. Yool A.J. J. Neurosci. 2006; 26: 7811-7819Crossref PubMed Scopus (79) Google Scholar). both the pathway (2Anthony T.L. Brooks H.L. Boassa D. Leonov S. Yanochko G.M. Regan J.W. Yool A.W. Mol. Pharmacol. 2000; 57: 576-588Crossref PubMed Scopus (144) Google Scholar, 3Yool A.J. Stamer D. Regan J.W. Science. 1996; 273: 1216-1218Crossref PubMed Scopus (141) Google and the PKC pathway described in this study a increase of both ionic conductance and water permeability. this study that protein kinase C positively regulates channels with a predominant role of both PKC phosphorylation sites Thr157 and This new pathway of AQP1 regulation is independent of the previously described cyclic nucleotide Activation of AQP1 may contribute to the PKC-dependent stimulation of physiological processes that are by AQP1 such as endothelial permeability, angiogenesis, and urine concentration. The AQP1 was by and for with and and for and AQP1 The of and is