Anisomycin downregulates gap-junctional intercellular communication via the p38 MAP-kinase pathway

Area of Science:

• Cellular Biology
• Molecular Biology
• Biochemistry

Background:

• Connexin 43 (Cx43) phosphorylation, particularly by extracellular signal-regulated kinase, reduces gap-junctional intercellular communication (GJIC).
• The role of p38 mitogen-activated protein (MAP) kinase in regulating GJIC remains unclear, despite observed reductions in GJIC in its presence.

Purpose of the Study:

• To investigate the mechanism by which p38 MAP kinase activation affects GJIC.
• To determine the role of Cx43 phosphorylation in anisomycin-induced changes in GJIC.

Main Methods:

• Utilized fluorescence recovery after photobleaching assays to measure GJIC in WB-F344 cells.
• Employed immunohistochemistry to assess Cx43 protein localization at cell borders.
• Conducted total protein labeling with [(35)S]-methionine and Cx43 labeling with [(32)P]-orthophosphates.

Main Results:

• Anisomycin treatment decreased GJIC and depleted phosphorylated Cx43, with reduced Cx43 at cell borders.
• SB203580, a p38 MAP kinase inhibitor, prevented the loss of phosphorylated Cx43 and its localization at cell borders.
• Anisomycin increased Cx43 phosphorylation levels but decreased the amount of phosphorylated Cx43, suggesting accelerated degradation. GJIC reduction was independent of protein synthesis inhibition.

Conclusions:

• p38 MAP kinase activation leads to a reduction in phosphorylated Cx43 levels, likely through enhanced degradation.
• The loss of phosphorylated Cx43 is responsible for the decrease in gap junction numbers and GJIC.
• SB203580 effectively preserves GJIC by inhibiting p38 MAP kinase-mediated Cx43 degradation.