Modulation of junctional permeability

Area of Science:

• Cell biology
• Biophysics
• Physiology

Background:

• Intercellular coupling, essential for coordinating cellular functions, can be altered through dynamic changes in intercellular channels.
• Increased intracellular calcium ([Ca2+]i) and changes in intracellular pH (pHi) are known to affect cell-to-cell communication, leading to decoupling.
• The precise mechanisms by which Ca2+ and H+ physiologically modulate gap junction conductance remain unclear.

Purpose of the Study:

• To investigate the roles of intracellular calcium and pH in regulating intercellular communication.
• To explore the proposed cyclic AMP (cAMP)-calcium hypothesis for modulating junctional permeability.
• To elucidate potential feedback mechanisms between calcium and cAMP in controlling junctional conductance.

Main Methods:

• The study discusses mechanisms of intercellular coupling modulation, including channel synthesis/destruction and permeability changes.
• It examines the impact of increased intracellular calcium ([Ca2+]i), induced by sodium-calcium exchange or metabolic inhibition, on cell decoupling.
• The dependence of gap junction conductance on intracellular pH (pHi) in embryonic cells is highlighted.

Main Results:

• Increased free [Ca2+]i leads to cell decoupling.
• Gap junction conductance in embryonic cells is highly sensitive to pHi.
• The study presents the cyclic AMP (cAMP)-calcium hypothesis, suggesting cAMP modulates junctional permeability via kinases.

Conclusions:

• While increased [Ca2+]i and altered pHi affect cell coupling, their exact physiological roles in modulating junctional conductance require further investigation.
• The cAMP-calcium hypothesis proposes a mechanism where cAMP, through kinases, influences junctional permeability.
• A potential feedback loop between calcium and cAMP may be crucial for the physiological regulation of junctional conductance.