Upregulation of the large conductance voltage- and Ca2+-activated K+ channels by Janus kinase 2.
The iberiotoxin-sensitive large conductance voltage- and Ca(2+)-activated potassium (BK) channels (maxi-K(+)-channels) hyperpolarize the cell membrane thus supporting Ca(2+) entry through Ca(2+)-release activated Ca(2+) channels. Janus kinase-2 (JAK2) has been identified as novel regulator of ion transport. To explore whether JAK2 participates in the regulation of BK channels, cRNA encoding Ca(2+)-insensitive BK channels (BK(M513I+Δ899-903)) was injected into Xenopus oocytes with or without cRNA encoding wild-type JAK2, gain-of-function (V617F)JAK2, or inactive (K882E)JAK2. K(+) conductance was determined by dual electrode voltage clamp and BK-channel protein abundance by confocal microscopy. In A204 alveolar rhabdomyosarcoma cells, iberiotoxin-sensitive K(+) current was determined utilizing whole cell patch clamp. A204 cells were further transfected with JAK2 and BK-channel transcript, and protein abundance was quantified by RT-PCR and Western blotting, respectively. As a result, the K(+) current in BK(M513I+Δ899-903)-expressing oocytes was significantly increased following coexpression of JAK2 or (V617F)JAK2 but not (K882E)JAK2. Coexpression of the BK channel with (V617F)JAK2 but not (K882E)JAK2 enhanced BK-channel protein abundance in the oocyte cell membrane. Exposure of BK-channel and (V617F)JAK2-expressing oocytes to the JAK2 inhibitor AG490 (40 μM) significantly decreased K(+) current. Inhibition of channel insertion by brefeldin A (5 μM) decreased the K(+) current to a similar extent in oocytes expressing the BK channel alone and in oocytes expressing the BK channel and (V617F)JAK2. The iberiotoxin (50 nM)-sensitive K(+) current in rhabdomyosarcoma cells was significantly decreased by AG490 pretreatment (40 μM, 12 h). Moreover, overexpression of JAK2 in A204 cells significantly enhanced BK channel mRNA and protein abundance. In conclusion, JAK2 upregulates BK channels by increasing channel protein abundance in the cell membrane.
Department of Physiology, University of Tübingen, Tübingen, Germany; and.
Zohreh
Z
Hosseinzadeh
Department of Physiology, University of Tübingen, Tübingen, Germany; and.
Ahmad
A
Almilaji
Department of Physiology, University of Tübingen, Tübingen, Germany; and.
Sabina
S
Honisch
Department of Physiology, University of Tübingen, Tübingen, Germany; and.
Tatsiana
T
Pakladok
Department of Physiology, University of Tübingen, Tübingen, Germany; and.
GuoXing
G
Liu
Department of Physiology, University of Tübingen, Tübingen, Germany; and.
Shefalee K
SK
Bhavsar
Institute of Pharmacy, Department of Pharmacology and Toxicology, University of Tübingen, Tübingen, Germany.
Peter
P
Ruth
Department of Physiology, University of Tübingen, Tübingen, Germany; and.
Ekaterina
E
Shumilina
Department of Physiology, University of Tübingen, Tübingen, Germany; and florian.lang@uni-tuebingen.de.
Florian
F
Lang
D000818:Animals; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D006801:Humans; D053614:Janus Kinase 2 / Q000096:biosynthesis*; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000096:biosynthesis*; D051379:Mice; D024681:Potassium Channels, Calcium-Activated / Q000096:biosynthesis; D015854:Up-Regulation / Q000502:physiology*; D014982:Xenopus laevis
D051036:Large-Conductance Calcium-Activated Potassium Channels; D024681:Potassium Channels, Calcium-Activated; C507924:JAK2 protein, human; D053614:Janus Kinase 2
BK channel; JAK2; JAK2 inhibitor AG490; tumor cells