Hsp20, a novel protein of the Toxoplasma gondii pellicle

NATALIA DE MIGUEL, MARYSE LEBRU, AOIFE HEASLIP, MARIANA MATRAJT, JEAN FRANCOIS DUBREMETZ & SERGIO O. ANGE

Montana, USA

Congreso; Ninth International Congress on Toxoplasmosis; 2007

The pellicle of T. gondii parasite is a unique triple bilayer structure, consisting of the plasma membrane and two tightly apposed membranes of the underlying inner membrane complex (IMC). Membrane skeletons are structural elements that provide mechanical support to the plasma membrane and define cell shape. This function is performed by the subpellicular network, assembled at an early stage in the development of daughter parasites. Here, we characterize the ultrastructural localization of a small heat shock protein (Hsp20) in the membrane skeleton of the parasite. Indirect immunofluorescence analysis showed that the protein is localized in the IMC, similar as observed with other important cytoskeleton components like IMC1 or Gap45. The anti-Hsp20 antibody also recognizes the subpellicular network of daughter parasites in replicating tachyzoites. Electron microscope examination of tachyzoites reveals the presence of Hsp20 associated with the outer face of the IMC, on the side facing the plasma membrane, similar as glideosome proteins. Generation of transgenic Hsp20 mutants showed that the N-terminal part of the sequence is necessary but not sufficient for membrane targeting. Although the physiological function of Hsp20 protein is unknown, the localization of Hsp20 may therefore contribute to protect membranes of the IMC under stress conditions, however, further investigations are needed to understand its role in the biology of the parasite.