An extracellular loop of the human non-gastric H,K-ATPase alpha-subunit is involved in apical plasma membrane polarization.
The human non-gastric H,K-ATPase, ATP1AL1, belongs to the gene family of P-type ATPases. Consistent with their physiological roles in ion transport, members of this group, including the Na,KATPase and the gastric and non-gastric H,K-ATPases, are differentially polarized to either the basolateral or apical plasma membrane in epithelial cells. However, their polarized distribution is highly complex and depends on specific sorting signals or motifs which are recognized by the subcellular targeting machinery. For the gastric H,K-ATPase it has been suggested that the 4(th) transmembrane spanning domain (TM4) and its flanking regions induce conformational sorting motifs which direct the ion pump exclusively to the epithelial apical membrane. Here, we show in transfected Madin-Darby canine kidney (MDCK) cells that the related non-gastric H,KATPase, ATP1AL1, does contain similar sorting motifs in close proximity to TM4. A short extracellular loop between TM3 and TM4 is critical for this pump's apical delivery. A single point mutation in the corresponding region redirects ATP1AL1 to the basolateral membrane. In conclusion, our work provides further evidence that the cellular distribution of P-type ATPases is determined by conformational sorting motifs.
Lerner
Markus
M
Department of Physiology, University of Münster.
Lemke
Dieter
D
Bertram
Helga
H
Schillers
Hermann
H
Oberleithner
Hans
H
Caplan
Michael J
MJ
Reinhardt
Jürgen
J
D000595:Amino Acid Sequence; D000818:Animals; D019921:Biotinylation; D015153:Blotting, Western; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D017506:H(+)-K(+)-Exchanging ATPase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D018613:Microscopy, Confocal; D017354:Point Mutation / Q000235:genetics; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D011993:Recombinant Fusion Proteins; D017506:H(+)-K(+)-Exchanging ATPase