Mutations of Cx43 that affect B cell spreading in response to BCR signaling
Letitia Falk1, May Dang-Lawson, José Luis Vega
1CELL and I-cubed (I) Research Groups, Life Sciences Institute, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada.
Abstract:
The gap junction (GJ) protein connexin 43 (Cx43) is both necessary and sufficient for B cell receptor (BCR)-mediated cell spreading. To address how Cx43 mediates this effect, we blocked its function genetically, by expressing mutants of Cx43, and pharmacologically, by using chemical inhibitors. While various point mutations of Cx43 inhibited B cell spreading, treatment with channel blocking drugs did not, suggesting that this response was independent of channel function. The critical region of Cx43 appears to be the cytoplasmic carboxyl-terminal (CT) domain, which has previously been shown to be important for B cell spreading. Consistent with this, mutations of either tyrosine 247 or 265 found in the CT were sufficient to inhibit spreading. Thus Cx43 may influence B cell spreading by mechanisms requiring protein binding to, or modification of, these sites in the CT tail.
Insights
Connexin 43 (Cx43) protein is crucial for B cell receptor-mediated cell spreading. Its function in this process is independent of its channel activity, highlighting the importance of its carboxyl-terminal domain.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- B cell receptor (BCR) signaling is critical for adaptive immunity.
- Gap junction (GJ) proteins, particularly connexin 43 (Cx43), play roles in cell communication and signaling.
- Cx43 has been implicated in B cell function, but its precise mechanism in BCR-mediated cell spreading is unclear.
Purpose of the Study:
- To elucidate the mechanism by which Cx43 mediates B cell receptor (BCR)-mediated cell spreading.
- To determine if Cx43 channel function is required for B cell spreading.
- To identify the critical regions of Cx43 involved in this cellular response.
Main Methods:
- Utilized genetic approaches by expressing Cx43 mutants in B cells.
- Employed pharmacological inhibition of Cx43 channel function.
- Assessed B cell spreading following BCR stimulation.
Main Results:
- Various point mutations in Cx43 inhibited B cell spreading.
- Pharmacological blockade of Cx43 channel function did not affect B cell spreading.
- Mutations within the cytoplasmic carboxyl-terminal (CT) domain, specifically at tyrosine 247 or 265, abolished B cell spreading.
Conclusions:
- Cx43 mediates BCR-induced B cell spreading through a mechanism independent of its channel activity.
- The carboxyl-terminal (CT) domain of Cx43 is critical for this function.
- Cx43 likely influences B cell spreading via protein interactions or modifications within its CT domain.
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