title: PPTX, a pentraxin domain-containing protein, interacts with the T1 domain of K v 4.
abstract: Voltage-gated K(+) (K(v)) channels reside as tetramers in the membrane. The events that coordinate folding, trafficking, and tetramerization are mediated by an array of associated proteins and phospholipids whose identification is vital to understanding the dynamic nature of channel expression and activity. An interaction between an A-type K(+) channel, K(v)4.2, and a protein containing a pentraxin domain (PPTX) was demonstrated in the cochlea (Duzhyy et al. [ 2005] J. Biol. Chem. 280:15165-15172). Here, we present results based on fold recognition and homology modeling that revealed the tetramerization (T1) domain of K(v)4.2 as a potential docking site for interacting proteins such as PPTX. By using this model, putative sites were experimentally tested with the yeast two-hybrid system to assay interactions between PPTX and the T1 domain of K(v)4.2 wild type (wt) and mutants (mut). Results showed that amino acid residues 86 and 118 in the T1 domain are essential for interaction, because replacing these negatively charged with neutrally charged amino acids inhibits interactions. Cotransfections of Chinese hamster ovary cells with PPTX and K(v)4.2wt further revealed that PPTX increases K(v)4.2 wt expression in vitro when analyzing total lysates, whereas interactions with K(v)4.2 microt resulted in a decrease. These studies suggest that portions of the T1 domain can act as docking sites for proteins such as PPTX, further underscoring the significance of this domain.
authors.affiliation: Department of Otolaryngology-HNS, Otology Laboratory, University of South Florida College of Medicine, Tampa, Florida 33612, USA.
authors.forename: Margaret
authors.initials: M
authors.lastname: Harvey
authors.forename: Joerg
authors.initials: J
authors.lastname: Karolat
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Sakai
authors.forename: Bernd
authors.initials: B
authors.lastname: Sokolowski
mesh_terms: D000818:Animals; D002097:C-Reactive Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016466:CHO Cells; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002645:Chickens; D003051:Cochlea / Q000166:cytology / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D015640:Ion Channel Gating / Q000502:physiology; D051605:Kv Channel-Interacting Proteins / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology; D008958:Models, Molecular; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae; D011984:Sensory Receptor Cells / Q000166:cytology / Q000378:metabolism*; D000683:Serum Amyloid P-Component / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051672:Shal Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013136:Spiral Ganglion / Q000166:cytology / Q000378:metabolism*; D013329:Structure-Activity Relationship; D020798:Two-Hybrid System Techniques; D000099153:Pentraxins
chemical_list: D002097:C-Reactive Protein; D002352:Carrier Proteins; D051605:Kv Channel-Interacting Proteins; D009419:Nerve Tissue Proteins; D000683:Serum Amyloid P-Component; D051672:Shal Potassium Channels; D000099153:Pentraxins