Functional characterization of canine connexin45

Area of Science:

• Molecular Biology
• Cardiovascular Physiology
• Biophysics

Background:

• Gap junctional proteins, specifically connexins, are crucial for intercellular communication in the heart.
• Canine ventricular myocytes express connexin 43 (Cx43), connexin 45 (Cx45), and connexin 40 (Cx40).
• Understanding the functional properties and interactions of these connexins is vital for comprehending cardiac electrophysiology.

Purpose of the Study:

• To characterize the functional properties of canine connexin 45 (Cx45).
• To investigate the functional interactions between Cx45 and Cx43 in heterotypic gap junctions.
• To determine the voltage and pH sensitivity of Cx45-containing gap junctions.

Main Methods:

• Functional characterization of canine Cx45 using Xenopus oocyte pairs.
• Assessment of homotypic (Cx45/Cx45) and heterotypic (Cx45/Cx43, Cx45/Cx38) gap junction coupling.
• Measurement of junctional currents to analyze voltage dependence and pH sensitivity.

Main Results:

• Homotypic Cx45 channels exhibited robust electrical coupling.
• Heterotypic channels formed by Cx45 with Cx43 or Cx38 also displayed high conductance.
• Junctional currents in heterotypic channels showed asymmetrical voltage dependence, with Cx45-mediated gating influenced by relative negativity.

Conclusions:

• Canine Cx45 forms functional homotypic and heterotypic gap junctions with Cx43 and Cx38.
• Cx45-containing heterotypic channels exhibit unique voltage-dependent gating properties, suggesting a role in regulating cardiac electrical activity.
• Differences in pH sensitivity between homotypic and heterotypic Cx45/Cx43 channels highlight the complexity of gap junction regulation.