The calcium-binding EF-hand in polycystin-L is not a domain for channel activation and ensuing inactivation.
Polycystin-L (PCL) shares high homology with polycystin-2, the product of polycystic kidney disease gene-2. It was previously shown that the PCL forms a non-selective cation channel activated by calcium influx. However, it remains unclear whether calcium activates/inactivates PCL by binding to the EF-hand motif located on the cytoplasmic carboxyl-terminus. Here we obtained two PCL splice variants from liver (PCL-LV, lacking the EF-hand) and testis (PCL-TS, lacking 45 amino acids on the carboxyl tail) using PCR-based approaches. When expressed in Xenopus oocytes and studied using electrophysiology both splice variants exhibited basal cation channel activity and calcium-induced channel activation. While PCL-TS displayed similar activation to PCL, PCL-LV exhibited a three-fold increased activation. All five PCL C-terminal artificial truncation mutants also exhibited basal and calcium-activated channel activities, in particular the mutant T622X lacking the EF-hand was associated with increased activation. Our data demonstrate that the EF-hand and other parts of the carboxyl tail of PCL are not determinants of channel activation/inactivation although the EF-hand seems to be involved in the modulation of these processes.
Li
Qiang
Q
Department of Physiology, University of Alberta, 729 MSB, T6G 2H7, Edmonton, AB, Canada.
Liu
Yan
Y
Zhao
Wei
W
Chen
Xing-Zhen
XZ
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D015220:Calcium Channels; D003001:Cloning, Molecular; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007473:Ion Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009865:Oocytes / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016891:Polycystic Kidney, Autosomal Dominant / Q000235:genetics; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D050396:TRPP Cation Channels; D014981:Xenopus
D015220:Calcium Channels; D007473:Ion Channels; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D010750:Phosphoproteins; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D050396:TRPP Cation Channels; C117185:PKD2L1 protein, human