KChIP3 rescues the functional expression of Shal channel tetramerization mutants.
KChIP proteins regulate Shal, Kv4.x, channel expression by binding to a conserved sequence at the N terminus of the subunit. The binding of KChIP facilitates a redistribution of Kv4 protein to the cell surface, producing a large increase in current along with significant changes in channel gating kinetics. Recently we have shown that mutants of Kv4.2 lacking the ability to bind an intersubunit Zn(2+) between their T1 domains fail to form functional channels because they are unable to assemble to tetramers and remain trapped in the endoplasmic reticulum. Here we find that KChIPs are capable of rescuing the function of Zn(2+) site mutants by driving the mutant subunits to assemble to tetramers. Thus, in addition to known trafficking effects, KChIPs play a direct role in subunit assembly by binding to monomeric subunits within the endoplasmic reticulum and promoting tetrameric channel assembly. Zn(2+)-less Kv4.2 channels expressed with KChIP3 demonstrate several distinct kinetic changes in channel gating, including a reduced time to peak and faster entry into the inactivated state as well as extending the time to recover from inactivation by 3-4 fold.
Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030, USA.
Kumud
K
Kunjilwar
Candace
C
Strang
David
D
DeRubeis
Paul J
PJ
Pfaffinger
D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000502:physiology*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D006224:Cricetinae; D004553:Electric Conductivity; D004721:Endoplasmic Reticulum; D015870:Gene Expression; D049452:Green Fluorescent Proteins / Q000235:genetics; D015640:Ion Channel Gating; D007700:Kinetics; D051605:Kv Channel-Interacting Proteins; D018613:Microscopy, Confocal; D016296:Mutagenesis; D024642:Potassium Channels, Voltage-Gated / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology; D017510:Protein Folding; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D051672:Shal Potassium Channels; D013329:Structure-Activity Relationship; D015032:Zinc / Q000378:metabolism
D002135:Calcium-Binding Proteins; C497020:Kcnd2 protein, rat; C496760:Kcnip3 protein, rat; D051605:Kv Channel-Interacting Proteins; D024642:Potassium Channels, Voltage-Gated; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D051672:Shal Potassium Channels; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D015032:Zinc