Cysteine string protein limits expression of the large conductance, calcium-activated K⁺ (BK) channel.
Large-conductance, calcium-activated K(+) (BK) channels are widely distributed throughout the nervous system and play an essential role in regulation of action potential duration and firing frequency, along with neurotransmitter release at the presynaptic terminal. We have previously demonstrated that select mutations in cysteine string protein (CSPα), a presynaptic J-protein and co-chaperone, increase BK channel expression. This observation raised the possibility that wild-type CSPα normally functions to limit neuronal BK channel expression. Here we show by Western blot analysis of transfected neuroblastoma cells that when BK channels are present at elevated levels, CSPα acts to reduce expression. Moreover, we demonstrate that the accessory subunits, BKβ4 and BKβ1 do not alter CSPα-mediated reduction of expressed BKα subunits. Structure-function analysis reveals that the N-terminal J-domain of CSPα is critical for the observed regulation of BK channels levels. Finally, we demonstrate that CSPα limits BK current amplitude, while the loss-of-function homologue CSPαHPD-AAA increases BK current. Our observations indicate that CSPα has a role in regulating synaptic excitability and neurotransmission by limiting expression of BK channels.
Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
Eva
E
Ahrendt
Libin Cardiovascular Institute, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada.
Barry
B
Kyle
Libin Cardiovascular Institute, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada.
Andrew P
AP
Braun
Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
Janice E A
JE
Braun
D000818:Animals; D019921:Biotinylation; D015153:Blotting, Western; D045744:Cell Line, Tumor; D005786:Gene Expression Regulation / Q000187:drug effects*; D050956:HSP40 Heat-Shock Proteins / Q000378:metabolism* / Q000494:pharmacology; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism* / Q000494:pharmacology; D051379:Mice; D018408:Patch-Clamp Techniques; D017729:Presynaptic Terminals / Q000378:metabolism*; D013329:Structure-Activity Relationship
D050956:HSP40 Heat-Shock Proteins; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008565:Membrane Proteins; C088460:cysteine string protein