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Microarray Analysis of Ion Transport‐Related Genes in Reissner’s Membrane
Author(s) -
Raveendran Nithya N.,
Wu Tao,
Pondugula Satyanarayana R.,
Marcus Daniel C.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a345-b
Subject(s) - epithelial sodium channel , pendrin , amiloride , chemistry , gerbil , microbiology and biotechnology , ion transporter , protein subunit , apical membrane , biology , medicine , gene , biochemistry , transporter , membrane , sodium , organic chemistry , ischemia
Reissner’s membrane (RM) plays an important role in ion homeostasis of the cochlea; disregulation is thought to be involved in Meniere’s disease, a syndrome that is often treated with glucocorticoids. We demonstrated currents across gerbil RM that could be accounted for by active absorption of Na via apical epithelial Na channels (ENaC), basolateral K channels & Na,K‐ATPase [Lee & Marcus, Neurosci . 2003]. We sought molecular evidence for mRNA expression of key elements of this pathway in rat and mouse RM using gene microarray and quantitative RT‐PCR. Rat RM showed the same amiloride‐sensitive Isc as in gerbil. Dexamethasone (DEX) led to an up‐regulation of α‐ENaC by a factor of 3 although the α1 subunit of Na,K‐ATPase was unchanged. Gene array showed that DEX up‐regulated all 3 subunits of ENaC (α: 3x; β : 1.2x; γ : 1.5x) and the α2 subunit of Na,K‐ATPase in mouse RM. Transcripts for β 1, 2 & 3‐Na,K‐ATPase were slightly down‐regulated. Other important genes in this pathway (sgk1, glucocorticoid receptor, Nedd 4‐2, 11β HSD‐1) were also present. RM has also been indirectly implicated in anion transport. Indeed, we found transcripts present for anion transporters (Na/K/2Cl‐ cotransporter; pendrin; anion exchanger‐1,‐2,‐3,‐4; Cl channels) and cAMP regulation (PKA, cAMP‐dependent GEF, adenylyl cyclase, phosphodiesterase). These results support our earlier finding of an active amiloride‐sensitive Na absorptive function in gerbil RM, extend these results to rat and mouse RM, demonstrate that this pathway is under control of glucocorticosteroids and provide a molecular basis for possible Cl transport function. NIH‐NIDCD grants R01‐DC00212, NCRR P20 RR17686 & P20 RR16475.