title: AKAP220 manages apical actin networks that coordinate aquaporin-2 location and renal water reabsorption.
abstract: Filtration through the kidney eliminates toxins, manages electrolyte balance, and controls water homeostasis. Reabsorption of water from the luminal fluid of the nephron occurs through aquaporin-2 (AQP2) water pores in principal cells that line the kidney-collecting duct. This vital process is impeded by formation of an "actin barrier" that obstructs the passive transit of AQP2 to the plasma membrane. Bidirectional control of AQP2 trafficking is managed by hormones and signaling enzymes. We have discovered that vasopressin-independent facets of this homeostatic mechanism are under the control of A-Kinase Anchoring Protein 220 (AKAP220; product of the Akap11 gene). CRISPR/Cas9 gene editing and imaging approaches show that loss of AKAP220 disrupts apical actin networks in organoid cultures. Similar defects are evident in tissue sections from AKAP220-KO mice. Biochemical analysis of AKAP220-null kidney extracts detected reduced levels of active RhoA GTPase, a well-known modulator of the actin cytoskeleton. Fluorescent imaging of kidney sections from these genetically modified mice revealed that RhoA and AQP2 accumulate at the apical surface of the collecting duct. Consequently, these animals are unable to appropriately dilute urine in response to overhydration. We propose that membrane-proximal signaling complexes constrained by AKAP220 impact the actin barrier dynamics and AQP2 trafficking to ensure water homeostasis.
authors.affiliation: Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195; Department of Pharmacology, University of Washington, Seattle, WA 98195.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Whiting
authors.affiliation: Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195; Department of Pharmacology, University of Washington, Seattle, WA 98195.
authors.forename: Leah
authors.initials: L
authors.lastname: Ogier
authors.affiliation: Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195; Department of Pharmacology, University of Washington, Seattle, WA 98195.
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Forbush
authors.affiliation: Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195; Department of Pharmacology, University of Washington, Seattle, WA 98195.
authors.forename: Paula
authors.initials: P
authors.lastname: Bucko
authors.affiliation: Department of Pharmacology, University of Washington, Seattle, WA 98195.
authors.forename: Janani
authors.initials: J
authors.lastname: Gopalan
authors.affiliation: Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195; Department of Pharmacology, University of Washington, Seattle, WA 98195.
authors.forename: Ole-Morten
authors.initials: OM
authors.lastname: Seternes
authors.affiliation: Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195; Department of Pharmacology, University of Washington, Seattle, WA 98195.
authors.forename: Lorene K
authors.initials: LK
authors.lastname: Langeberg
authors.affiliation: Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195; Department of Pharmacology, University of Washington, Seattle, WA 98195 scottjdw@uw.edu.
authors.forename: John D
authors.initials: JD
authors.lastname: Scott
mesh_terms: D054758:A Kinase Anchor Proteins / Q000235:genetics / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000818:Animals; D051399:Aquaporin 2 / Q000378:metabolism*; D005260:Female; D006706:Homeostasis; D007668:Kidney / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000378:metabolism; D008297:Male; D018345:Mice, Knockout; D009924:Organ Culture Techniques; D065608:Renal Reabsorption; D014867:Water / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
chemical_list: D054758:A Kinase Anchor Proteins; D000199:Actins; C560627:Akap11 protein, mouse; D051399:Aquaporin 2; D014867:Water; D020742:rhoA GTP-Binding Protein
keywords: A-Kinase Anchoring Protein; kidney physiology; signal transduction