Downregulation of KCNQ4 by Janus Kinase 2

• Published in: The Journal of membrane biology Vol. 246; no. 4; pp. 335 - 341
• Main Authors: Hosseinzadeh, Zohreh, Sopjani, Mentor, Pakladok, Tatsiana, Bhavsar, Shefalee K., Lang, Florian
• Format: Journal Article
• Language: English
• Published: New York Springer-Verlag 01.04.2013; Springer Nature B.V
• Subjects: Animals; Biochemistry; Biomedical and Life Sciences; Brefeldin A - pharmacology; Cell Size - drug effects; Cellular biology; Erythropoietin - metabolism; Female; Gene expression; Human Physiology; Janus Kinase 2 - antagonists & inhibitors; Janus Kinase 2 - metabolism; KCNQ Potassium Channels - antagonists & inhibitors; KCNQ Potassium Channels - metabolism; Kinases; Life Sciences; Membranes; Oocytes - drug effects; Oocytes - metabolism; Tyrphostins - pharmacology; Xenopus; channel; Cell volume regulation; K; Erythropoietin; JAK2; Leptin
• ISSN: 0022-2631; 1432-1424
• DOI: 10.1007/s00232-013-9537-8

Janus kinase-2 (JAK2) participates in the signaling of several hormones, growth factors and cytokines. Further stimulators of JAK2 include osmotic cell shrinkage, and the kinase activates the cell volume regulatory Na + /H + exchanger. The kinase may thus participate in cell volume regulation. Cell shrinkage is known to inhibit K + channels. Volume-regulatory K + channels include the voltage-gated K + channel KCNQ4. The present study explored the effect of JAK2 on KCNQ4 channel activity. KCNQ4 was expressed in Xenopus oocytes with or without wild-type JAK2, constitutively active V617F JAK2 or inactive K882E JAK2; and cell membrane conductance was determined by dual-electrode voltage clamp. Expression of KCNQ4 was followed by the appearance of voltage-gated K + conductance. Coexpression of JAK2 or of V617F JAK2, but not of K882E JAK2, resulted in a significant decrease in conductance. Treatment of KCNQ4 and JAK2 coexpressing oocytes with the JAK2 inhibitor AG490 (40 μM) was followed by an increase in conductance. Treatment of KCNQ4 expressing oocytes with brefeldin A (5 μM) was followed by a decrease in conductance, which was similar in oocytes expressing KCNQ4 together with JAK2 as in oocytes expressing KCNQ4 alone. Thus, JAK2 apparently does not accelerate channel protein retrieval from the cell membrane. In conclusion, JAK2 downregulates KCNQ4 activity and thus counteracts K + exit, an effect which may contribute to cell volume regulation.