The cytoplasmic C-terminal fragment of polycystin-1 regulates a Ca2+-permeable cation channel.
The cytoplasmic C-terminal portion of the polycystin-1 polypeptide (PKD1(1-226)) regulates several important cell signaling pathways, and its deletion suffices to cause autosomal dominant polycystic kidney disease. However, a functional link between PKD1 and the ion transport processes required to drive renal cyst enlargement has remained elusive. We report here that expression at the Xenopus oocyte surface of a transmembrane fusion protein encoding the C-terminal portion of the PKD1 cytoplasmic tail, PKD1(115-226), but not the N-terminal portion, induced a large, Ca(2+)-permeable cation current, which shifted oocyte reversal potential (E(rev)) by +33 mV. Whole cell currents were sensitive to inhibition by La(3+), Gd(3+), and Zn(2+), and partially inhibited by SKF96365 and amiloride. Currents were not activated by bath hypertonicity, but were inhibited by acid pH. Outside-out patches pulled from PKD1(115-226)-expressing oocytes exhibited a 5.1-fold increased NP(o) of endogenous 20-picosiemens cation channels of linear conductance. PKD1(115-226)-injected oocytes also exhibited elevated NP(o) of unitary calcium currents in outside-out and cell-attached patches, and elevated calcium permeability documented by fluorescence ratio and (45)Ca(2+) flux experiments. Both Ca(2+) conductance and influx were inhibited by La(3+). Mutation of candidate phosphorylation sites within PKD1(115-226) abolished the cation current. We conclude that the C-terminal cytoplasmic tail of PKD1 up-regulates inward current that includes a major contribution from Ca(2+)-permeable nonspecific cation channels. Dysregulation of these or similar channels in autosomal dominant polycystic kidney disease may contribute to cyst formation or expansion.
Vandorpe
D H
DH
Molecular Medicine and Renal Units, Beth Israel Deaconess Medical Center, Department of Medicine, Harvard Medical School, Boston, Massachusetts 02215, USA.
Chernova
M N
MN
Jiang
L
L
Sellin
L K
LK
Wilhelm
S
S
Stuart-Tilley
A K
AK
Walz
G
G
Alper
S L
SL
D000595:Amino Acid Sequence; D000818:Animals; D015220:Calcium Channels / Q000378:metabolism* / Q000502:physiology; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology*; D010539:Permeability; D011506:Proteins / Q000737:chemistry*; D050396:TRPP Cation Channels; D014981:Xenopus
D015220:Calcium Channels; D010446:Peptide Fragments; D011506:Proteins; D050396:TRPP Cation Channels