Heparan sulfate proteoglycan triggers focal adhesion kinase signaling during Trypanosoma cruzi invasion

BACKGROUND Trypanosoma cruzi, the etiologic agent of Chagas disease, is capable of triggering different signaling pathways that modulate its internalisation in mammalian cells. Focal adhesion kinase (FAK), a non-receptor tyrosine kinase protein, has been demonstrated as a mechanism of T. cruzi invasion in cardiomyocytes. Since the involved cell surface receptors are not yet known, we evaluated whether heparan sulfate proteoglycans (HSPG), a molecule involved in T. cruzi recognition and in the regulation of multiple signaling pathways, are able to trigger the FAK signaling pathway during T. cruzi invasion. METHODS To investigate the role of HSPG in the regulation of the FAK signaling pathway during trypomastigote entry, we performed heparan sulfate (HS) depletion from the cardiomyocyte surface by treatment with heparinase I or p-nitrophenyl- β-D-xylopyranoside (p-n-xyloside), which abolishes glycosaminoglycan (GAG) attachment to the proteoglycan core protein. Wild-type (CHO-k1) and GAG-deficient Chinese hamster ovary cells (CHO-745) were also used as an approach to evaluate the participation of the HSPG-FAK signaling pathway. FAK activation (FAK Tyr397) and spatial distribution were analysed by immunoblotting and indirect immunofluorescence, respectively. FINDINGS HS depletion from the cardiomyocyte surface inhibited FAK activation by T. cruzi. Cardiomyocyte treatment with heparinase I or p-n-xyloside resulted in 34% and 28% FAK phosphorylation level decreases, respectively. The experiments with the CHO cells corroborated the role of HSPG as a FAK activation mediator. T. cruzi infection did not stimulate FAK phosphorylation in CHO-745 cells, leading to a 36% reduction in parasite invasion. FAK inhibition due to the PF573228 treatment also impaired T. cruzi entry in CHO-k1 cells. MAIN CONCLUSION Jointly, our data demonstrate that HSPG is a key molecule in the FAK signaling pathway activation, regulating T. cruzi entry.