TDK conference 2013

Nowadays the effects of the secondary metabolites come into sight since they can influence animals or humans but the biological consequence is poorly understood. Ophiobolin is a member of the ophiobolin complex of secondary fungal metabolites in the seeds of feeds. We compared the expression and distribution of Kv4 channels and their modulators in cardiomyopathic heart and in the presence of ophiobolin AOP1 (AOP1) as an external stress factor for myocytes.We studied the organization of Kv4 type ion channels at cellular level in cardiac myocytes by means of immunocytochemistry with light- and electron microscopy and confocal microscopy. Our aim was to study the expression of Kv4.2 and Kv4.3 ion channels with regulator element in the presence of AOP1 on the heart cells. We used rat heart tissues and H9c2 rat heart cell cultures with various microscopic and molecular biology methods. Our first observation is that the Kv4.3 pattern is different from that of Kv4.2: only Kv4.3 was localized in the Z-line where the T-tubular system is located in the cardiac muscle. Ophiobolin P1 treatments down-regulated and redistributed both the Kv4.2 and Kv4.3 ion channels not only in the plasma membrane but in the cell organelles, mainly around the mitochondria and nuclear membrane. Furthermore we found that the synapse-associated protein 97 (SAP97) does not colocalize with Kv4.x ion channel α-subunits at the sarcolemma as compared to the controls. The SAP97 and Kv4 channel subunits colocalize at the sarcolemma of healthy cardiomyocytes and the distribution of these complexes has changed under ophiobolin treatment. These results strongly suggest that the anchoring and modulator functions of SAP97 are crucial for maintaining the normal ITO current in the heart tissues. The tripartite complex of Kv4.3-SAP97-CAMKII structure is needed to form the physiologically active Kv4 type channels being essential to regulate the subcellular localization of channels in the cardiomyocytes.

This work was support by grants OTKA NI-6190 and TÁMOP-4.2.2.A-11/1/KONV-2012-0035.