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Article: Molecular basis of isoform-specific μ-conotoxin block of cardiac, skeletal muscle, and brain Na+ channels

TitleMolecular basis of isoform-specific μ-conotoxin block of cardiac, skeletal muscle, and brain Na+ channels
Authors
KeywordsChemicals And Cas Registry Numbers
Issue Date2003
PublisherAmerican Society for Biochemistry and Molecular Biology, Inc. The Journal's web site is located at http://www.jbc.org/
Citation
Journal Of Biological Chemistry, 2003, v. 278 n. 10, p. 8717-8724 How to Cite?
Abstractμ-Conotoxins (μ-CTXs) block skeletal muscle Na+ channels with an affinity 1-2 orders of magnitude higher than cardiac and brain Na+ channels. Although a number of conserved pore residues are recognized as critical determinants of μ-CTX block, the molecular basis of isoform-specific toxin sensitivity remains unresolved. Sequence comparison of the domain II (DII) S5-S6 loops of rat skeletal muscle (μ1, Nav1.4), human heart (hh1, Nav1.5), and rat brain (rb1, Nav1.1) Na+ channels reveals substantial divergence in their N-terminal S5-P linkers even though the P-S6 and C-terminal P segments are almost identical. We used Nav1.4 as the backbone and systematically converted these DII S5-P isoform variants to the corresponding residues in Nav1.1 and Nav1.5. The Nav1.4→Nav1.5 variant substitutions V724R, C725S, A728S, D730S, and C731S (Nav1.4 numbering) reduced block of Nav1.4 by 4-, 86-, 12-, 185-, and 55-fold respectively, rendering the skeletal muscle isoform more "cardiac-like." Conversely, an Nav1.5→ Nav1.4 chimeric construct in which the Nav1.4 DII S5-P linker replaces the analogous segment in Nav1.5 showed enhanced μ-CTX block. However, these variant determinants are conserved between Nav1.1 and Nav1.4 and thus cannot explain their different sensitivities to μ-CTX. Comparison of their sequences reveals two variants at Nav1.4 positions 729 and 732: Ser and Asn in Nav1.4 compared with Thr and Lys in Nav1.1, respectively. The double mutation S729T/N732K rendered Nav1.4 more "brain-like" (30-fold ↓ in block), and the converse mutation T925S/K928N in Nav1.1 reproduced the high affinity blocking phenotype of Nav1.4. We conclude that the DII S5-P linker, although lying outside the conventional ion-conducting pore, plays a prominent role in μ-CTX binding, thus shaping isoform-specific toxin sensitivity.
Persistent Identifierhttp://hdl.handle.net/10722/91635
ISSN
2015 Impact Factor: 4.258
2015 SCImago Journal Rankings: 3.151
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorLi, RAen_HK
dc.contributor.authorEnnis, ILen_HK
dc.contributor.authorXue, Ten_HK
dc.contributor.authorNguyen, HMen_HK
dc.contributor.authorTomaselli, GFen_HK
dc.contributor.authorGoldin, ALen_HK
dc.contributor.authorMarbán, Een_HK
dc.date.accessioned2010-09-17T10:22:33Z-
dc.date.available2010-09-17T10:22:33Z-
dc.date.issued2003en_HK
dc.identifier.citationJournal Of Biological Chemistry, 2003, v. 278 n. 10, p. 8717-8724en_HK
dc.identifier.issn0021-9258en_HK
dc.identifier.urihttp://hdl.handle.net/10722/91635-
dc.description.abstractμ-Conotoxins (μ-CTXs) block skeletal muscle Na+ channels with an affinity 1-2 orders of magnitude higher than cardiac and brain Na+ channels. Although a number of conserved pore residues are recognized as critical determinants of μ-CTX block, the molecular basis of isoform-specific toxin sensitivity remains unresolved. Sequence comparison of the domain II (DII) S5-S6 loops of rat skeletal muscle (μ1, Nav1.4), human heart (hh1, Nav1.5), and rat brain (rb1, Nav1.1) Na+ channels reveals substantial divergence in their N-terminal S5-P linkers even though the P-S6 and C-terminal P segments are almost identical. We used Nav1.4 as the backbone and systematically converted these DII S5-P isoform variants to the corresponding residues in Nav1.1 and Nav1.5. The Nav1.4→Nav1.5 variant substitutions V724R, C725S, A728S, D730S, and C731S (Nav1.4 numbering) reduced block of Nav1.4 by 4-, 86-, 12-, 185-, and 55-fold respectively, rendering the skeletal muscle isoform more "cardiac-like." Conversely, an Nav1.5→ Nav1.4 chimeric construct in which the Nav1.4 DII S5-P linker replaces the analogous segment in Nav1.5 showed enhanced μ-CTX block. However, these variant determinants are conserved between Nav1.1 and Nav1.4 and thus cannot explain their different sensitivities to μ-CTX. Comparison of their sequences reveals two variants at Nav1.4 positions 729 and 732: Ser and Asn in Nav1.4 compared with Thr and Lys in Nav1.1, respectively. The double mutation S729T/N732K rendered Nav1.4 more "brain-like" (30-fold ↓ in block), and the converse mutation T925S/K928N in Nav1.1 reproduced the high affinity blocking phenotype of Nav1.4. We conclude that the DII S5-P linker, although lying outside the conventional ion-conducting pore, plays a prominent role in μ-CTX binding, thus shaping isoform-specific toxin sensitivity.en_HK
dc.languageengen_HK
dc.publisherAmerican Society for Biochemistry and Molecular Biology, Inc. The Journal's web site is located at http://www.jbc.org/en_HK
dc.relation.ispartofJournal of Biological Chemistryen_HK
dc.subjectChemicals And Cas Registry Numbersen_HK
dc.subject.meshAmino Acid Sequenceen_HK
dc.subject.meshAnimalsen_HK
dc.subject.meshBrain - drug effects - metabolismen_HK
dc.subject.meshConotoxins - pharmacologyen_HK
dc.subject.meshHumansen_HK
dc.subject.meshMolecular Sequence Dataen_HK
dc.subject.meshMuscle, Skeletal - drug effects - metabolismen_HK
dc.subject.meshMutagenesis, Site-Directeden_HK
dc.subject.meshMyocardium - metabolismen_HK
dc.subject.meshProtein Isoforms - antagonists & inhibitors - chemistry - geneticsen_HK
dc.subject.meshRatsen_HK
dc.subject.meshSequence Homology, Amino Aciden_HK
dc.subject.meshSodium Channels - chemistry - drug effects - geneticsen_HK
dc.titleMolecular basis of isoform-specific μ-conotoxin block of cardiac, skeletal muscle, and brain Na+ channelsen_HK
dc.typeArticleen_HK
dc.identifier.emailLi, RA:ronaldli@hkucc.hku.hken_HK
dc.identifier.authorityLi, RA=rp01352en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1074/jbc.M210882200en_HK
dc.identifier.pmid12471026en_HK
dc.identifier.scopuseid_2-s2.0-0037424267en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0037424267&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume278en_HK
dc.identifier.issue10en_HK
dc.identifier.spage8717en_HK
dc.identifier.epage8724en_HK
dc.identifier.isiWOS:000181466800124-
dc.publisher.placeUnited Statesen_HK
dc.identifier.scopusauthoridLi, RA=7404724466en_HK
dc.identifier.scopusauthoridEnnis, IL=6604033332en_HK
dc.identifier.scopusauthoridXue, T=7005064190en_HK
dc.identifier.scopusauthoridNguyen, HM=7403321926en_HK
dc.identifier.scopusauthoridTomaselli, GF=7005223451en_HK
dc.identifier.scopusauthoridGoldin, AL=7103401202en_HK
dc.identifier.scopusauthoridMarbán, E=8075977300en_HK

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