Taken together, these data suggest that in the young adult mouse there is a specific, functional selection and assembly of NKA subunit isoforms in the SV lateral wall, which is disrupted and dys-regulated with age. that the 1-1 heterodimer is the selective preferential heterodimer over the 1-2 heterodimer in cochlea lateral wall. Interestingly, pathway experiments utilizing cultured mouse cochlear marginal cells from the HA130 SV (SV-K1 cells) indicated that decreased mRNA and protein expressions of 1 1, 1 and 2 subunit isoforms are not associated with reduction of NKA activity following application of ouabain, but ouabain did disrupt the 1-1 heterodimer interaction. Lastly, the association between the 1 and 1 subunit isoforms was present in the cochlear lateral wall of young adult mice, but this interaction could not be detected in old mice. Taken together, these data suggest HA130 that in the young adult mouse there is a specific, functional selection and assembly of NKA subunit isoforms in the SV lateral wall, which is disrupted and dys-regulated with age. Interventions for this age-linked ion channel disruption may have the potential to help diagnose, prevent, or treat age-related hearing loss. transfection studies have demonstrated that each a subunit isoform can partner with a subunit to form a functional antiporter enzyme. Selective co-immunoprecipitation of and subunits suggests there is a preferred binding partner for the co-assembly of these subunits, and this preferential binding may be related to the tissue type and differences in the functional roles of the NKA isoforms, such as K+ affinity and isoform stability (Colonna et al., 1997a,b; Schmalzing et al., 1997; Tokhtaeva et al., 2012a,b). NKA is expressed ubiquitously in most cells, and theoretically, each of the four subunit isoforms can interact with each of the three subunit isoforms to form an active unit. However, not all isoforms are expressed simultaneously in a single cell or tissue type, and their configurations depend on their functional roles. HA130 The and heterodimer configurations can have different tissue-specific forms. For example, 1-1 NKA is a monomer combination present in most cell types (Tokhtaeva et al., 2012a, b), whereas the 2 2 isoforms are found primarily in muscle and nervous system tissues (Sweadner, 1989; Kaplan, 2002; Lingrel, 2010; Blanco and Mercer, 1998; Blanco, 2005); 3 isoforms are expressed mainly in neurons (McLean et al., 2009; Dobretsov and Stimers, 2005), whereas the 4 isoforms reside only in the testis (Woo et al., 2000; Jimenez et al., 2011). The 2 2 isoforms are expressed predominantly in brain and muscle (Lingrel, 2010; Blanco, 2005), while the 3 isoforms are located in lung, testis, skeletal muscle and liver (Malik et al., 1996; Arystarkhova and Sweadner, 1997, Rabbit Polyclonal to PIAS1 1996). NKA carries out many cellular functions, such as modulating a cells resting potential, promoting ion transport, controlling cell volume, and functioning as a signal transducer (Hall and Guyton, 2006; Yuan et al., 2005; Li et al., 2009). The enzyme also regulates contractility of cardiac, smooth, and skeletal muscle, modulates blood pressure under stress, and affects intercellular adhesion in epithelia (Blaustein et al., 2009; Rindler et HA130 al., 2011; Tokhtaeva et al., 2012a,b). Moreover, a third subunit, small membrane proteins FXYD, have been shown to be associated with the complex of NKA. FXYD proteins are a small group of seven transmembrane proteins, which are localized in tissues and organs involved in solute and fluid transport, where they are proposed to act as regulators of ion transport. All members of this family are known to associate with NKA and modulate its properties in a tissue- and isoform-specific way. In rat, FXYD6 was found HA130 to be co-localized with NKA in the stria vascularis and to be expressed in rat in various epithelial cells bordering the endolymphatic.