title: ENaC channels in oocytes from Xenopus laevis and their regulation by xShroom1 protein.
abstract: Shroom is a family of related proteins linked to the actin cytoskeleton. xShroom1 is constitutively expressed in X. oocytes and is required for the expression of amiloride sensitive sodium channels (ENaC). Oocytes were injected with α, β, and γ mENaC and xShroom1 sense or antisense oligonucleotides. We used voltage clamp techniques to study the amiloride-sensitive Na(+) currents (INa((amil))). We observed a marked reduction in INa((amil)) in oocytes co-injected with xShroom1 antisense. Oocytes expressing a DEG mutant β-mENaC subunit (β-S518K) with an open probability of 1 had enhanced INa((amil)) although these currents were also reduced when co-injected with xShroom1 antisense. Addition of low concentration (20 ng/ml) of trypsin which activates the membrane-resident ENaC channels led to a slow increase in INa((amil)) in oocytes with xShroom1 sense but had no effect on the currents in oocytes coinjected with ENaC and xShroom1 antisense. The same results were obtained with higher concentrations of trypsin (2 μg/ml) exposed during 2.5 min. In addition, fluorescence positive staining of plasma membrane in the oocytes expressing α, β and γ mENaC and xShroom1 sense were observed but not in oocytes coinjected with ENaC and xShroom1 antisense oligonucleotides. On this basis, we suggest that xShroom1-dependent ENaC inhibition may be through the number of channels inserted in the membrane.
authors.affiliation: Laboratorio de Canales Iónicos, Instituto de Investigaciones Médicas Alfredo Lanari, University of Buenos Aires, IDIM- CONICET, Buenos Aires, Argentina.
authors.forename: Yanina A
authors.initials: YA
authors.lastname: Assef
authors.forename: Marcelo
authors.initials: M
authors.lastname: Ozu
authors.forename: Gabriela I
authors.initials: GI
authors.lastname: Marino
authors.forename: Luciano
authors.initials: L
authors.lastname: Galizia
authors.forename: Basilio A
authors.initials: BA
authors.lastname: Kotsias
mesh_terms: D000818:Animals; D053503:Epithelial Sodium Channels / Q000235:genetics / Q000378:metabolism*; D005260:Female; D009154:Mutation; D016376:Oligonucleotides, Antisense / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism / Q000473:pathology / Q000502:physiology; D018408:Patch-Clamp Techniques; D015222:Sodium Channels / Q000235:genetics / Q000378:metabolism*; D014357:Trypsin / Q000494:pharmacology; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis / Q000378:metabolism*
chemical_list: D053503:Epithelial Sodium Channels; D016376:Oligonucleotides, Antisense; C078824:Shroom1 protein, Xenopus; D015222:Sodium Channels; D029867:Xenopus Proteins; D014357:Trypsin