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Functional analysis of human cardiac gap junction channel mutants
G I Fishman1, A P Moreno, D C Spray
1Department of Medicine, Albert Einstein College of Medicine, Bronx, NY 10461.
Summary
The cytoplasmic tail of connexin43 (Cx43) significantly influences gap junction channel conductance, but not voltage sensitivity. Truncated Cx43 mutants alter single-channel properties, revealing the tail
Area of Science:
- Molecular Biology
- Cell Biology
- Biophysics
Background:
- Connexins are membrane proteins forming gap junction channels.
- Channel properties depend on the specific connexin isoform.
- Human heart primarily expresses connexin43 (Cx43).
Purpose of the Study:
- Investigate the molecular basis of Cx43 gap junction channel behavior.
- Determine the role of the Cx43 cytoplasmic tail domain.
Main Methods:
- Site-directed mutagenesis to create truncated Cx43 mutants.
- Transfection into communication-deficient SKHep1 cells.
- Measurement of unitary conductance and voltage sensitivity.
Main Results:
- Truncated Cx43 mutants restored intercellular coupling.
- Mutants exhibited altered unitary conductance values (160 and 50 pS).
- Voltage sensitivity of Cx43 channels was not affected by tail truncation.
Conclusions:
- The Cx43 cytoplasmic tail domain is a key determinant of unitary conductance.
- Voltage dependence of gap junction channels is independent of the Cx43 tail.
- Phosphorylation sites in the tail may not be essential for channel assembly.