Role of adaptor proteins and clathrin in the trafficking of human kidney anion exchanger 1 (kAE1) to the cell surface.
Kidney anion exchanger 1 (kAE1) plays an important role in acid-base homeostasis by mediating chloride/bicarbornate (Cl-/HCO3-) exchange at the basolateral membrane of α-intercalated cells in the distal nephron. Impaired intracellular trafficking of kAE1 caused by mutations of SLC4A1 encoding kAE1 results in kidney disease - distal renal tubular acidosis (dRTA). However, it is not known how the intracellular sorting and trafficking of kAE1 from trans-Golgi network (TGN) to the basolateral membrane occurs. Here, we studied the role of basolateral-related sorting proteins, including the mu1 subunit of adaptor protein (AP) complexes, clathrin and protein kinase D, on kAE1 trafficking in polarized and non-polarized kidney cells. By using RNA interference, co-immunoprecipitation, yellow fluorescent protein-based protein fragment complementation assays and immunofluorescence staining, we demonstrated that AP-1 mu1A, AP-3 mu1, AP-4 mu1 and clathrin (but not AP-1 mu1B, PKD1 or PKD2) play crucial roles in intracellular sorting and trafficking of kAE1. We also demonstrated colocalization of kAE1 and basolateral-related sorting proteins in human kidney tissues by double immunofluorescence staining. These findings indicate that AP-1 mu1A, AP-3 mu1, AP-4 mu1 and clathrin are required for kAE1 sorting and trafficking from TGN to the basolateral membrane of acid-secreting α-intercalated cells.
Division of Molecular Medicine, Department of Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Mutita
M
Junking
Nunghathai
N
Sawasdee
Natapol
N
Duangtum
Boonyarit
B
Cheunsuchon
Thawornchai
T
Limjindaporn
Pa-thai
PT
Yenchitsomanus
D033942:Adaptor Proteins, Vesicular Transport / Q000502:physiology*; D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002462:Cell Membrane / Q000378:metabolism; D002966:Clathrin / Q000502:physiology*; D017931:DNA Primers; D004285:Dogs; D057809:HEK293 Cells; D006801:Humans; D061985:Madin Darby Canine Kidney Cells; D021381:Protein Transport; D034741:RNA, Small Interfering
D033942:Adaptor Proteins, Vesicular Transport; D001457:Anion Exchange Protein 1, Erythrocyte; D002966:Clathrin; D017931:DNA Primers; D034741:RNA, Small Interfering; C454201:SLC4A1 protein, human
basolateral sorting protein; distal renal tubular acidosis; kidney anion exchanger 1; protein trafficking; protein-protein interaction