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potassium voltage-gated channel, delayed-rectifier, subfamily S, member 2
KV9.2 is member 2 of subfamily S of potassium voltage-gated delayed-rectifier channels, encoded by the gene KCNS2.
Voltage-gated potassium channels form the largest and most diversified class of ion channels and are present in both excitable and nonexcitable cells. Their main functions are associated with the regulation of the resting membrane potential and the control of the shape and frequency of action potentials. The alpha subunits are of 2 types: those that are functional by themselves and those that are electrically silent but capable of modulating the activity of specific functional alpha subunits. The protein encoded by this gene is not functional by itself but can form heteromultimers with member 1 and with member 2 (and possibly other members) of the Shab-related subfamily of potassium voltage-gated channel proteins. This gene belongs to the S subfamily of the potassium channel family. 
In contrast to the genes in the other subfamilies, members of the Kv8 and Kv9 subfamilies have been found to be incapable of forming functional channels when expressed either in oocytes or cell lines. Moreover, these mammalian genes appear to have no Drosophila homologs. 
Kcns2 : potassium voltage-gated channel, delayed-rectifier, subfamily S, member 2
Kv2.1 and Kv2.2
Kv9.1 and Kv9.2 colocalized with Kv2.1 and/or Kv2.2 α subunits in several regions of the brain and alters the Kv2's kinetics as well 
Structure of Kv9.2 ion Channel
The ORFs of Kv9.1 and Kv9.2 encode proteins of 497 and 477 amino acids, respectively, with a calculated molecular mass of 54.9 and 54.3 kDa (Fig. 1 A). Protein sequences reveal that all the structural characteristics of outward rectifier voltage-gated K+ channel α subunits (Kv) are conserved in Kv9.1 and Kv9.2, i.e. six putative transmembrane segments (S1 to S6), a transmembrane region (S4) showing five positively charged amino acids and a conserved pore-forming region (named H5 or P domain). As indicated in Fig. 1 A, Kv9.1 and Kv9.2 subunits contain several putative phosphorylation sites located in the cytoplasmic regions for protein kinase C, cAMP-dependent protein kinase, Ca2+-calmodulin kinase II, casein kinase II, and tyrosine kinase. No N-glycosylation sequence was detected 
Kv9.1 and Kv9.2 are neuronal modulatory alpha subunits that define a structural family designated as Kv9. They modulate Kv2.alpha subunits but have no functional activity by themselves. 
Kv9.2 Expressed Exclusively in the Brain
Northern blot analysis presented in Fig.2 shows that Kv9.1 and Kv9.2 mRNAs are expressed only in the brain. Specific probes detected two transcripts for Kv9.1 with an estimated size of 2.2 and 2.7 kb and one for Kv9.2 of approximately 5.3 kb. No expression was observed in heart, spleen, lung, liver, skeletal muscle, kidney, or testis 
Kv9.1 and Kv9.2, two known members of the Kv9 subfamily, appear to be expressed diffusely in cells of the inferior colliculus .
K+ channel functions are included in very diverse processes such as neuronal integration, cardiac pacemaking, muscle contraction, and hormone secretion in excitable cells , as well as in cell proliferation, cell volume regulation, and lymphocyte differentiation .
Kv9.1 and Kv9.2 modulate Kv2.alpha subunits but have no functional activity by themselves . I.e., the kinetics of activation and the voltage-dependence of Kv2.1 currents are altered by such co-expression with Kv9.1 .
Kinetics of Kv9.2 with Kv2 Family
The time constant of activation of Kv2.1 was not modified by Kv9.1 but it was slightly increased by Kv9.2. No variation of the intensity of the remaining Kv2.1 current after a 9-s inactivation was recorded in the presence of Kv9.1 and Kv9.2. The image bellow shows that the normalized Kv2.2 currents are only slightly modified by Kv9.1 and Kv9.2. The time constant of activation of Kv2.2 was slightly decreased by Kv9.1 and not modified by Kv9.2 .
Editor : Admin.
Contributors : Rajnish Ranjan, Michael Schartner
To cite : [Editor], [Contributors]. Accessed on [Date] Channelpedia , http://channelpedia.epfl.ch/ionchannels/31