Role of PKC and AMPK in hypertonicity-stimulated water reabsorption in rat inner medullary collecting ducts

Abstract

Adrenomedullin (ADM) increases water permeability in the inner medullary collecting duct by mediating aquaporin‐2 (AQP2) phosphorylation. It is generally considered to be a backup system for vasopressin. We investigated whether adrenomedullin stimulates osmotic water permeability through cAMP and/or protein kinase A (PKA). RNA sequencing and western analysis showed that ADM and its receptors, calcitonin‐receptor‐like receptor (CRLR) and receptor‐activity‐modifying proteins 2 or 3 (RAMP2 or RAMP3) are highly expressed in the inner medullary collecting ducts of control rats. No mRNA expression was seen for RAMP1. We measured water permeability in inner medullary collecting ducts of rats by tubule perfusion with and without treatment with the PDE4 inhibitor roflumilast or the PKA inhibitor H89. ADM significantly increased osmotic water permeability from 251.4 ± 58.1 to 383.4 ± 73.2 μm/s (n=4, p<0.05). Roflumilast (30nM) further increased ADM‐stimulated osmotic water permeability to 472.7 ± 84.9 μm/s (n=4, p<0.05). Inhibition of PKA by H89 decreased ADM‐stimulated osmotic water permeability from 225.4 ± 57.3 to 179.7 ± 49.6 μm/s (n=3, p<0.05). Western analysis with phospho‐specific antibody showed that ADM significantly increased phosphorylation of AQP2 at serine 256 and decreased phosphorylation of AQP2 at serine 261. We conclude that ADM and its receptors are expressed in inner medulla and that the mechanism of ADM stimulation of water reabsorption involves cAMP and activation of PKA. Further, our results suggest that ADM may represent a complimentary method for vasopressin in regulating water homeostasis. Support or Funding Information This work was supported by Emory URC grant 00067457, and AHA Career Development Grant #18CDA34060053. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Tea Drinking Alleviates Diabetic Symptoms via Upregulating Renal Water Reabsorption Proteins and Downregulating Renal Gluconeogenic Enzymes in db/db Mice

“…PKC‐α knockout mice have defective urine concentration. [ 41 ] The mechanisms of action of PKC‐α in enhancing urine concentration include: 1) PKC‐α regulates urea permeability, [ 42–44 ] 2) PKC‐α upregulates AQP2 through phosphorylating cyclic adenosine binding protein, which is a transcriptional factor of AQP2, [ 21,22 ] 3) PKC‐α promotes vasopressin‐stimulated AQP2 trafficking via altering microtubule assembly, [ 23 ] 4) PKC decreases phosphorylation of AQP2 at Ser261, [ 24 ] which inversely regulates AQP2 trafficking, [ 45,46 ] and 5) PKC‐α increases phosphorylation of UT‐A1 at Ser494 [ 47 ] and enhances UT‐A1 cell surface expression. [ 25 ] In the present study, both GT and BT infusions increased renal PKC‐α and renal membrane PKC‐α in db/db mice.…”

“…[ 17–19 ] A high vasopressin level also favors the development of diabetic nephropathy. [ 20 ] In addition to being regulated by vasopressin, AQP2 and UT‐A1 are also under the regulation by other factors, such as protein kinase C‐α (PKC‐α) [ 21–25 ] or adenosine 5′‐monophosphate‐activated protein kinase. [ 26 ] However, the effects of vasopressin‐independent increase of renal water reabsorption proteins on polyuria have not been investigated in diabetes mellitus.…”

Antioxidant, antihyperglycemic, and antihyperlipidemic properties of Chimonanthus salicifolius S. Y. Hu leaves in experimental animals: modulation of thioredoxin and glutathione systems, renal water reabsorption, and gut microbiota

“…The kidney maintains glucose and body fluid homeostasis, and reabsorbs 99% of raw urine (about 180 L) produced by healthy adults per day. Renal water reabsorption-associated proteins, including UT-A1 and AQP2, regulated by PKC-α via phosphorylation of UT-A1 at Ser494 and AQP2 at Ser256 or dephosphorylation of AQP2 at Ser261 (62)(63)(64)(65)(66)(67), in medullary collecting ducts play an important role in maintaining body water homeostasis via promoting renal water reabsorption and urine concentration (68,69). For instance, lack of urea transporter UT-B adaptively increased the expression of AQP2 in UT-B null mice (69).…”

PKA‐independent vasopressin signaling in renal collecting duct

“…Activation of one or more SNF1‐subfamily kinases by vasopressin in PKA‐null mpkCCD cells may have implications with regard to the regulation of AQP2. Prior studies implicated AMPK in the regulation of AQP2 trafficking 41,42 and osmotic water transport 41,43 in the renal collecting duct. Furthermore, data from a cultured collecting duct cell line, MDCK, provided strong evidence for a central role of another SNF1‐subfamily kinase, viz.…”