Regulation of the ankyrin-B-based targeting pathway following myocardial infarction.

AIMS: Ion channel reorganization is a critical step in the pro-arrhythmogenic remodelling process that occurs in heart disease. Ankyrin-B (AnkB) is required for targeting and stabilizing ion channels, exchangers, and pumps. Despite a wealth of knowledge implicating the importance of AnkB in human cardiovascular physiology, nothing is known regarding the role of AnkB in common forms of acquired human disease. METHODS AND
RESULTS: We present the first report of AnkB regulation following myocardial infarction (MI). AnkB protein levels were reduced in the infarct border zone 5 days following coronary artery occlusion in the canine. We also observed a dramatic increase in AnkB mRNA levels 5 days post-occlusion. Surprisingly, the expression of the upstream AnkB cytoskeletal component beta2-spectrin was unchanged in post-infarct tissues. However, protein levels and/or membrane expression of downstream AnkB-associated ion channels and transporters Na+/K+ ATPase, Na+/Ca2+ exchanger, and IP3 receptor were altered 5 days post-occlusion. Interestingly, protein levels of the protein phosphatase 2A, an AnkB-associated signalling protein, were significantly affected 5 days post-occlusion. AnkB and PP2A protein levels recovered by 14 days post-occlusion, whereas Na+/K+ ATPase levels recovered by 2 months post-occlusion.
CONCLUSION: These findings reveal the first evidence of ankyrin remodelling following MI and suggest an unexpected divergence point for regulation between ankyrin and the underlying cytoskeletal network. These findings suggest a logical, but unexpected, molecular mechanism underlying ion channel and transporter remodelling following MI.