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Updated: Apr 5, 2026
Patch Clamp and Perfusion Techniques for Studying Ion Channels Expressed in Xenopus oocytes
Published on: January 10, 2011
Regulation of Large Conductance Voltage-and Ca2+-Activated K+ Channels by the Janus Kinase JAK3
Jamshed Warsi1, Yogesh Singh, Bernat Elvira
1Department of Physiology I, University of Tx00FC;bingen, Tx00FC;bingen, Germany.
Background/Aims:
Janus kinase 3 (JAK3), a tyrosine kinase contributing to the regulation of cell proliferation and apoptosis of lymphocytes and tumour cells, has been shown to modify the expression and function of several ion channels and transport proteins. Channels involved in the regulation of cell proliferation include the large conductance voltage- and Ca(2+)-activated K(+) channel BK. The present study explored whether JAK3 modifies BK channel protein abundance and current.
Methods:
cRNA encoding Ca(2+)-insensitive BK channel (BK(M513I+Δ899-903)) was injected into Xenopus oocytes with or without additional injection of cRNA encoding wild-type JAK3, constitutively active A568VJAK3, or inactive (K851A)JAK3. Voltage gated K(+ )channel activity was measured utilizing dual electrode voltage clamp. Moreover, BK channel protein abundance was determined utilizing flow cytometry in CD19(+) B lymphocyte cell membranes from mice lacking functional JAK3 (jak3(-/-)) and corresponding wild-type mice (jak3(+/+)).
Results:
BK activity in BK(M513I+Δ899-903) expressing oocytes was slightly but significantly decreased by coexpression of wild-type JAK3 and of (A568V)JAK3, but not by coexpression of (K851A)JAK3. The BK channel protein abundance in the cell membrane was significantly higher in jak3(-/-) than in jak3(+/+) B lymphocytes. The decline of conductance in BK and JAK3 coexpressing oocytes following inhibition of channel protein insertion by brefeldin A (5 µM) was similar in oocytes expressing BK with JAK3 and oocytes expressing BK alone, indicating that JAK3 might slow channel protein insertion into rather than accelerating channel protein retrieval from the cell membrane.
Conclusion:
JAK3 is a weak negative regulator of membrane BK protein abundance and activity.
Insights
Janus kinase 3 (JAK3) weakly reduces the abundance and activity of the large conductance calcium-activated potassium channel (BK). This suggests JAK3 plays a role in regulating BK channel expression and function in lymphocytes.
Area of Science:
- Molecular Biology
- Cell Physiology
- Immunology
Background:
- Janus kinase 3 (JAK3) is a tyrosine kinase involved in lymphocyte and tumor cell proliferation and apoptosis.
- JAK3 influences the expression and function of ion channels and transport proteins.
- The large conductance voltage- and Ca(2+)-activated K(+) channel (BK) is implicated in regulating cell proliferation.
Purpose of the Study:
- To investigate whether JAK3 affects the protein abundance and activity of the BK channel.
- To explore the regulatory role of JAK3 in BK channel function.
Main Methods:
- cRNA encoding a Ca(2+)-insensitive BK channel mutant was injected into Xenopus oocytes.
- Oocytes were co-injected with cRNA for wild-type, constitutively active, or inactive JAK3.
- BK channel activity was measured using dual electrode voltage clamp.
- BK channel protein abundance was assessed via flow cytometry in JAK3-deficient and wild-type mouse B lymphocytes.
Main Results:
- Co-expression of JAK3 with the BK channel mutant in oocytes significantly decreased BK channel activity.
- BK channel protein abundance was significantly higher in B lymphocytes lacking JAK3 compared to wild-type.
- Data suggest JAK3 may slow BK channel protein insertion into the membrane rather than accelerating retrieval.
Conclusions:
- JAK3 acts as a weak negative regulator of BK channel protein abundance and activity.
- JAK3 influences the membrane expression and function of the BK channel.
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