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Down-regulation of K⁺ channels by human parvovirus B19 capsid protein VP1
Musaab Ahmed1, Ahmad Almilaji1, Carlos Munoz1
1Department of Physiology, University of Tübingen, Germany.
Abstract:
Parvovirus B19 (B19V) can cause inflammatory cardiomyopathy and endothelial dysfunction. Pathophysiological mechanisms involved include lysophosphatidylcholine producing phospholipase A2 (PLA2) activity of the B19V capsid protein VP1. Most recently, VP1 and lysophosphatidylcholine have been shown to inhibit Na(+)/K(+) ATPase. The present study explored whether VP1 modifies the activity of Kv1.3 and Kv1.5 K(+) channels. cRNA encoding Kv1.3 or Kv1.5 was injected into Xenopus oocytes without or with cRNA encoding VP1 isolated from a patient suffering from fatal B19V-induced myocarditis. K(+) channel activity was determined by dual electrode voltage clamp. Injection of cRNA encoding Kv1.3 or Kv1.5 into Xenopus oocytes was followed by appearance of Kv K(+) channel activity, which was significantly decreased by additional injection of cRNA encoding VP1, but not by additional injection of cRNA encoding PLA2-negative VP1 mutant (H153A). The effect of VP1 on Kv current was not significantly modified by transcription inhibitor actinomycin (10 μM for 36 h) but was mimicked by lysophosphatidylcholine (1 μg/ml). The B19V capsid protein VP1 inhibits host cell Kv channels, an effect at least partially due to phospholipase A2 (PLA) dependent formation of lysophosphatidylcholine.
Insights
Parvovirus B19 capsid protein VP1 inhibits potassium (K+) channels. This inhibition, linked to phospholipase A2 activity and lysophosphatidylcholine production, contributes to B19V-induced myocarditis.
Area of Science:
- Cardiovascular Science
- Virology
- Molecular Biology
Background:
- Parvovirus B19 (B19V) is linked to inflammatory cardiomyopathy and endothelial dysfunction.
- The B19V capsid protein VP1 exhibits phospholipase A2 (PLA2) activity, producing lysophosphatidylcholine.
- VP1 and lysophosphatidylcholine have been shown to inhibit Na+/K+ ATPase.
Purpose of the Study:
- To investigate the effect of B19V capsid protein VP1 on Kv1.3 and Kv1.5 potassium channels.
- To elucidate the role of VP1's PLA2 activity in modulating K+ channel function.
Main Methods:
- cRNA encoding Kv1.3 or Kv1.5, and VP1 (wild-type or H153A mutant) were injected into Xenopus oocytes.
- Potassium channel activity was measured using dual electrode voltage clamp.
- Effects of lysophosphatidylcholine and actinomycin were assessed.
Main Results:
- VP1 significantly decreased Kv1.3 and Kv1.5 channel activity in oocytes.
- The inhibitory effect of VP1 was dependent on its PLA2 activity (H153A mutant had no effect).
- Lysophosphatidylcholine mimicked VP1's inhibitory effect on K+ channels.
Conclusions:
- The B19V capsid protein VP1 inhibits host cell Kv channels.
- This inhibition is mediated, at least partially, by PLA2-dependent formation of lysophosphatidylcholine.
- VP1-induced K+ channel dysfunction may contribute to B19V-associated myocarditis.
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