title: Differential expression of potassium channels in placentas from normal and pathological pregnancies: targeting of the K(ir) 2.1 channel to lipid rafts.
abstract: Potassium channels play important physiological roles in human syncytiotrophoblasts (hSTBs) from placenta, an epithelium responsible for maternal-fetal exchange. Basal and apical plasma membranes differ in their lipid and protein composition, and the latter contains cholesterol-enriched microdomains. In placental tissue, the specific localization of potassium channels is unknown. Previously, we described two isolated subdomains from the apical membrane (MVM and LMVM) and their respective microdomains (lipid rafts). Here, we report on the distribution of K(ir)2.1, K(v)2.1, TASK-1, and TREK-1 in hSTB membranes and the lipid rafts that segregate them. Immunoblotting experiments showed that these channels are present mainly in the apical membrane from healthy hSTBs. Apical expression versus basal membrane was 84 and 16% for K(ir)2.1 and K(v)2.1, 60 and 30% for TREK-1, and 74 and 26% for TASK-1. Interestingly, K(v)2.1 showed differences between apical membrane subdomains: 26 ± 8% was located in the LMVM and 59 ± 9% in MVM. In pathological placentas, the expression distribution changed in the basal membrane: preeclampsia shifted to 50% and intrauterine growth restriction to 42% for TASK-1 and both pathologies increased to 25% for K(ir)2.1 and K(v)2.1, K(ir)2.1 appeared to be associated with rafts that were sensitive to cholesterol depletion in healthy, but not in pathological, placentas. K(v)2.1 and TREK-1 emerged in the nonraft fractions. The precise membrane localization of ion channels in hSTB membranes is necessary to understand the physiological events.
authors.affiliation: Departamento de Fisiología y Biofísica, Instituto de Ciencias Biomédicas-ICBM, Facultad de Medicina, Universidad de Chile, Casilla, 70005 Santiago 7, Chile. griquelm@med.uchile.cl
authors.forename: Gloria
authors.initials: G
authors.lastname: Riquelme
authors.forename: Nicole
authors.initials: N
authors.lastname: de Gregorio
authors.forename: Catalina
authors.initials: C
authors.lastname: Vallejos
authors.forename: Macarena
authors.initials: M
authors.lastname: Berrios
authors.forename: Bárbara
authors.initials: B
authors.lastname: Morales
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D021962:Membrane Microdomains / Q000378:metabolism*; D010920:Placenta / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism*; D024683:Potassium Channels, Tandem Pore Domain / Q000235:genetics / Q000378:metabolism; D011247:Pregnancy; D011248:Pregnancy Complications / Q000378:metabolism*
chemical_list: C489461:Kir2.1 channel; D024661:Potassium Channels, Inwardly Rectifying; D024683:Potassium Channels, Tandem Pore Domain; C103742:potassium channel protein TREK-1; D002784:Cholesterol