Mechanisms of Two Modulatory Actions of the Channel-binding Protein Slob on the Drosophila Slowpoke Calcium-dependent Potassium Channel

Slob57 is an ion channel auxiliary protein that binds to and modulates the Drosophila Slowpoke calcium-dependent potassium channel (dSlo). We reported recently that residues 1–39 of Slob57 comprise the key domain that both causes dSlo inactivation and shifts its voltage dependence of activation to m...

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Main Authors:	Zeng, Haoyu, Weiger, Thomas M., Fei, Hong, Levitan, Irwin B.
Format:	Online
Language:	English
Published:	The Rockefeller University Press 2006
Online Access:	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2151581/

id	pubmed-2151581
recordtype	oai_dc
spelling	pubmed-21515812008-01-17 Mechanisms of Two Modulatory Actions of the Channel-binding Protein Slob on the Drosophila Slowpoke Calcium-dependent Potassium Channel Zeng, Haoyu Weiger, Thomas M. Fei, Hong Levitan, Irwin B. Article Slob57 is an ion channel auxiliary protein that binds to and modulates the Drosophila Slowpoke calcium-dependent potassium channel (dSlo). We reported recently that residues 1–39 of Slob57 comprise the key domain that both causes dSlo inactivation and shifts its voltage dependence of activation to more depolarized voltages. In the present study we show that removal of residues 2–6 from Slob57 abolishes the inactivation, but the ability of Slob57 to rightward shift the voltage dependence of activation of dSlo remains. A synthetic peptide corresponding in sequence to residues 1–6 of Slob57 blocks dSlo in a voltage- and dose-dependent manner. Two Phe residues and at least one Lys residue in this peptide are required for the blocking action. These data indicate that the amino terminus of Slob57 directly blocks dSlo, thereby leading to channel inactivation. Further truncation to residue Arg16 eliminates the modulation of voltage dependence of activation. Thus these two modulatory actions of Slob57 are independent. Mutation within the calcium bowl of dSlo greatly reduces its calcium sensitivity (Bian, S., I. Favre, and E. Moczydlowski. 2001. Proc. Natl. Acad. Sci. USA. 98:4776–4781). We found that Slob57 still causes inactivation of this mutant channel, but does not shift its voltage dependence of activation. This result confirms further the independence of the inactivation and the voltage shift produced by Slob57. It also suggests that the voltage shift requires high affinity Ca2+ binding to an intact calcium bowl. Furthermore, Slob57 inhibits the shift in the voltage dependence of activation of dSlo evoked by Ca2+, and this inhibition by Slob57 is greater at higher free Ca2+ concentrations. These results implicate distinct calcium-dependent and -independent mechanisms in the modulation of dSlo by Slob. The Rockefeller University Press 2006-11 /pmc/articles/PMC2151581/ /pubmed/17074977 http://dx.doi.org/10.1085/jgp.200609653 Text en Copyright © 2006, The Rockefeller University Press This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
repository_type	Open Access Journal
institution_category	Foreign Institution
institution	US National Center for Biotechnology Information
building	NCBI PubMed
collection	Online Access
language	English
format	Online
author	Zeng, Haoyu Weiger, Thomas M. Fei, Hong Levitan, Irwin B.
spellingShingle	Zeng, Haoyu Weiger, Thomas M. Fei, Hong Levitan, Irwin B. Mechanisms of Two Modulatory Actions of the Channel-binding Protein Slob on the Drosophila Slowpoke Calcium-dependent Potassium Channel
author_facet	Zeng, Haoyu Weiger, Thomas M. Fei, Hong Levitan, Irwin B.
author_sort	Zeng, Haoyu
title	Mechanisms of Two Modulatory Actions of the Channel-binding Protein Slob on the Drosophila Slowpoke Calcium-dependent Potassium Channel
title_short	Mechanisms of Two Modulatory Actions of the Channel-binding Protein Slob on the Drosophila Slowpoke Calcium-dependent Potassium Channel
title_full	Mechanisms of Two Modulatory Actions of the Channel-binding Protein Slob on the Drosophila Slowpoke Calcium-dependent Potassium Channel
title_fullStr	Mechanisms of Two Modulatory Actions of the Channel-binding Protein Slob on the Drosophila Slowpoke Calcium-dependent Potassium Channel
title_full_unstemmed	Mechanisms of Two Modulatory Actions of the Channel-binding Protein Slob on the Drosophila Slowpoke Calcium-dependent Potassium Channel
title_sort	mechanisms of two modulatory actions of the channel-binding protein slob on the drosophila slowpoke calcium-dependent potassium channel
description	Slob57 is an ion channel auxiliary protein that binds to and modulates the Drosophila Slowpoke calcium-dependent potassium channel (dSlo). We reported recently that residues 1–39 of Slob57 comprise the key domain that both causes dSlo inactivation and shifts its voltage dependence of activation to more depolarized voltages. In the present study we show that removal of residues 2–6 from Slob57 abolishes the inactivation, but the ability of Slob57 to rightward shift the voltage dependence of activation of dSlo remains. A synthetic peptide corresponding in sequence to residues 1–6 of Slob57 blocks dSlo in a voltage- and dose-dependent manner. Two Phe residues and at least one Lys residue in this peptide are required for the blocking action. These data indicate that the amino terminus of Slob57 directly blocks dSlo, thereby leading to channel inactivation. Further truncation to residue Arg16 eliminates the modulation of voltage dependence of activation. Thus these two modulatory actions of Slob57 are independent. Mutation within the calcium bowl of dSlo greatly reduces its calcium sensitivity (Bian, S., I. Favre, and E. Moczydlowski. 2001. Proc. Natl. Acad. Sci. USA. 98:4776–4781). We found that Slob57 still causes inactivation of this mutant channel, but does not shift its voltage dependence of activation. This result confirms further the independence of the inactivation and the voltage shift produced by Slob57. It also suggests that the voltage shift requires high affinity Ca2+ binding to an intact calcium bowl. Furthermore, Slob57 inhibits the shift in the voltage dependence of activation of dSlo evoked by Ca2+, and this inhibition by Slob57 is greater at higher free Ca2+ concentrations. These results implicate distinct calcium-dependent and -independent mechanisms in the modulation of dSlo by Slob.
publisher	The Rockefeller University Press
publishDate	2006
url	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2151581/
_version_	1611424149012480000

Mechanisms of Two Modulatory Actions of the Channel-binding Protein Slob on the Drosophila Slowpoke Calcium-dependent Potassium Channel

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