title: Downregulation of ClC-2 by JAK2.
abstract: JAK2 (Janus kinase-2) is activated by cell shrinkage and may thus participate in cell volume regulation. Cell volume regulatory ion channels include the small conductance Cl(-) channels ClC-2. The present study thus explored whether JAK2 influences ClC-2 activity. To this end, ClC-2 was expressed in Xenopus oocytes with or without wild type JAK2, active (V617F)JAK2 or inactive (K882E)JAK2 and the Cl(-) channel activity determined by dual electrode voltage clamp. Expression of ClC-2 was followed by a marked increase of cell membrane conductance. The conductance was significantly decreased following coexpression of JAK2 or (V617F)JAK2, but not by coexpression of (K882E)JAK2. Exposure of the oocytes expressing ClC-2 together with (V617F)JAK2 to the JAK2 inhibitor AG490 (40 μM) resulted in a gradual increase of the conductance. According to chemiluminescence JAK2 decreased the channel protein abundance in the cell membrane. The decline of conductance in ClC-2 and (V617F)JAK2 coexpressing oocytes following inhibition of channel protein insertion by brefeldin A (5 μM) was similar in oocytes expressing ClC-2 with (V617F)JAK2 and oocytes expressing ClC-2 alone, indicating that (V617F)JAK2 might slow channel protein insertion into rather than accelerating channel protein retrieval from the cell membrane. In conclusion, JAK2 down-regulates ClC-2 activity and thus counteracts Cl(-) exit, an effect which may impact on cell volume regulation.
authors.affiliation: Department of Physiology I, University of Tübingen, Tübingen, Germany.
authors.forename: Zohreh
authors.initials: Z
authors.lastname: Hosseinzadeh
authors.forename: Shefalee K
authors.initials: SK
authors.lastname: Bhavsar
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D000818:Animals; D001483:Base Sequence; D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels / Q000502:physiology*; D017931:DNA Primers; D015536:Down-Regulation / Q000502:physiology*; D006801:Humans; D053614:Janus Kinase 2 / Q000235:genetics / Q000502:physiology*; D049449:Luminescence; D016297:Mutagenesis, Site-Directed; D014981:Xenopus
chemical_list: D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels; D017931:DNA Primers; D053614:Janus Kinase 2