Cardiac troponin, a component of the thin filament, consists of three subunits, cTnT (tropomyosin binding), cTnI (inhibitory) and cTnC (calcium binding). Troponin is the major regulator of the muscle contraction. It functions as a calcium sensor and mediates the calcium sensitivity of the contraction (actin-myosin interaction). In addition to that, this function is fine-tuned by multiple reversible phosphorylations of troponin. Most important is the phosphorylation throuth the protein kinase A after ß-adrenergic stimulationof cTnI at serine residues 22 and 23, localised in the N-terminal arm specific for the cardiac isoform of cTnI. This phosphorylation considerably contibutes to an increase of the relaxation rate of myofibrils.
In recent years, a set of mutations, among others in the cTnI gene, was identified in patients, which may cause familiar hypertrophic cardiomyopathy (FHC). FHC is one of the most common genetic cardiovascular diseases and is associated with a higher risk of heart failure and sudden cardiac death.
We study in particular the molecular effects of such mutations on troponin function. Our special interest focuses on the effects on the regulation of heart muscle contraction via the ß-adrenergic pathway.
Current projects:
- Influence of FHC inducing mutations/ cTnI-phosphorylation on the formation of the thin filament and intermolecular interactions between the components of the thin filament
- Studies on contraction and calcium transients (change in the intracellular calcium concentration during contraction) depending of FHC inducing mutations after ß1-/ß2-adrenergic stimulation
- Relevance of the soluble adenylyl cyclase in hypertrophy
- Influence of micro particles and NO on thefunction of adult rat cardiomyocytes
- Identification of binding partners of cTnI
Methods:
- Preparation of recombinant proteins and of proteins from tissue
- Reconstitution of protein complexes
- Peptide arrays
- Measurement of the actomyosin-ATPase activity
- Fluorescence labeling, immunofluorescence
- Preparation of adult rat cardiomyocytes
- Adenoviral gene transfer
- Contraction measurements on isolated cardiomyocytes
- Calcium transient measurements on isolated cardiomyocytes