Disarray of sarcomeric alpha-actinin in cardiomyocytes infected by Trypanosoma cruzi

Abstract

Infection with Trypanosoma cruzi causes acute myocarditis and chronic cardiomyopathy. Remarkable changes have been demonstrated in the structure and physiology of cardiomyocytes during infection by this parasite that may contribute to the cardiac dysfunction observed in Chagas' disease. We have investigated the expression of alpha-actinin, an actin-binding protein that plays a key role in the formation and maintenance of Z-lines, during the T. cruzi-cardiomyocyte interaction in vitro. Immunolocalization of alpha-actinin in control cardiomyocytes demonstrated a typical periodicity in the Z line of cardiac myofibrils, as well as its distribution at focal adhesion sites and along the cell-cell junctions. No significant changes were observed in the localization of alpha-actinin after 24 h of infection. In contrast, depletion of sarcomeric distribution of alpha-actinin occurred after 72 h in T. cruzi-infected cardiomyocytes, while no change occurred at focal adhesion contacts. Biochemical assays demonstrated a reduction of 46% and 32% in the expression of alpha-actinin after 24 h and 72 h of infection, respectively. Intracellular parasites were also stained with an anti-alpha-actinin antibody that recognized a protein of 78 kDa by Western blot. Taken together, our data demonstrate a degeneration of the myofibrils in cardiomyocytes induced by T. cruzi infection, rather than a disassembly of the I bands within sarcomeres.

Trypanosoma cruzi Infection Induces a Global Host Cell Response in Cardiomyocytes

“…Several molecules at the cardiomyocyte surface, including carbohydrates, fibronectin, and heparan sulfate proteoglycans, are involved in the parasite-host cell recognition and mediate the invasion process (3,4,7,8,45). Structural changes in cardiomyocytes observed during intracel-lular development of the parasite may contribute to a reduction of transmission of the contractile force and lead to alterations in function of the heart in Chagas' disease (1,37,38,39,46). Finally, T. cruzi-infected cardiomyocytes elicit a strong immune response, characterized by the production of the chemokines RANTES and macrophage inflammatory protein 2 and the cytokines gamma interferon (IFN-␥) and tumor necrosis factor alpha (TNF-␣), which triggers a potent nitric oxide-dependent trypanocidal activity (33).…”

Remodeling of the sarcomeric cytoskeleton in cardiac ventricular myocytes during heart failure and after cardiac resynchronization therapy

“…Cultured adult rat cardiomyocytes completely lose striation of α-actinin between 4–7 days [34]. In mouse cardiomyocytes, after 72 h of infection with the parasite Trypanosoma cruzi , the overall expression of α-actinin decreased by 32% [11]. Furthermore α-actinin completely lost its periodic arrangement and became localized to focal adhesion sites [11].…”

“…The genes ACTN-1 and ACTN-4 encode α-actinin isoforms that are expressed in non-muscle cells, where these isoforms of α-actinin contribute to the actin cytoskeleton. ACTN-2 and ACTN-3 encode isoforms specific to the Z-disks of sarcomeres found in striated muscle fibers [4, 9–11], with α-actinin-2 being the only cardiac specific isoform [4]. …”

“…Several cardiac diseases have been associated with remodeling of α-actinin and the Z-disk [9–12]. Melo et al demonstrated that Trypanosoma cruzi in mouse myocytes caused α-actinin distributions to lose their periodic structure and to localize to focal adhesion sites [11]. Hein et al found depositions of α-actinin-1 in failing myocardium [10], while Oxford et al showed an accumulation of electron dense material around Z-lines in canines with arrhythmogenic cardiomyopathy.…”

Regulation of extracellular matrix expression and distribution in Trypanosoma cruzi-infected cardiomyocytes

“…FN matrix assembly is dependent on an intact cytoskeleton (Wu et al, 1995), generating the tension required for expansion of compact FN dimers and exposure of FN-FN binding sites (Wierzbicka-Patynowski and Schwarzbauer, 2003). T. cruzi-infected CMs have a disorganized cytoskeleton with myofibrillar breakdown (Pereira et al, 1993;Melo et al, 2006;Taniwaki et al, 2006). Thus, we examined the effect of cytochalasin D and nocodazole on the FN matrix arrangement.…”