Neurotrophin Receptor TrkC Is an Entry Receptor for Trypanosoma cruzi in Neural, Glial, and Epithelial Cells

Abstract

Trypanosoma cruzi, the agent of Chagas' disease, infects a variety of mammalian cells in a process that includes multiple cycles of intracellular division and differentiation starting with host receptor recognition by a parasite ligand(s). Earlier work in our laboratory showed that the neurotrophin-3 (NT-3) receptor TrkC is activated by T. cruzi surface trans-sialidase, also known as parasite-derived neurotrophic factor (PDNF). However, it has remained unclear whether TrkC is used by T. cruzi to enter host cells. Here, we show that a neuronal cell line (PC12-NNR5) relatively resistant to T. cruzi became highly susceptible to infection when overexpressing human TrkC but not human TrkB.

Parasite-Derived Neurotrophic Factor/trans-Sialidase of Trypanosoma cruzi Links Neurotrophic Signaling to Cardiac Innate Immune Response

“…PDNF was cloned from the T. cruzi Silvio X-10/4 strain (GenBank accession number AJ002174), and an N-terminal short form of PDNF (sPDNF) that contains Trk-binding sites was expressed in Escherichia coli BL21(DE3) bacteria and purified by Niaffinity chromatography, as described previously (22,24,25,35). Buffers were prepared in sterile endotoxin-free water, and sPDNF preparations were found to have undetectable levels of endotoxin, as determined by the Limulus amebocyte assay.…”

“…(ii) Trk-binding activity is mimicked by a 24-mer synthetic peptide (33), and (iii) the neuraminidase/trans-sialidase binds and activates Trk receptors in sialic acid-deficient cells (25). Furthermore, after phosphorylation by Akt kinase, the enzyme promotes cell survival in the cytosol, where sialyl-conjugate substrates are absent (34).…”

“…The T. cruzi outer membrane parasite-derived neurotrophic factor (PDNF) and a short form that contains receptor-binding sites (sPDNF) (20,21) bind and activate nerve growth factor (NGF) receptor TrkA (22) and neurotrophin-3 (NT-3) receptor TrkC (23), triggering host cell survival events and parasite host cell entry (24,25). PDNF was identified in 1983 in our labs as neuraminidase (26) consequent to the discovery of sialic acid in T. cruzi (27,28).…”

Multigene Families in Trypanosoma cruzi and Their Role in Infectivity

“…The mechanism resides in a domain of 21 amino acids that binds to the nerve growth factor TrKA receptor and produces its autophosphorylation and thereby activates phosphatidylinositol 3-kinase/Akt antiapoptotic signaling (17,19,20). In this way, the interaction between PNDF and TrKC receptors, which are receptors for the entry of T. cruzi into neural, glial, and epithelial cells, was recently demonstrated (73,74). This function is independent of sialic acid, which was demonstrated through the use of sialic acid mutant CHO cells and by the ability of the parasite to trigger the Akt response in the host cell cytosol, where there is no sialic acid available to the parasite, upregulating prosurvival mechanisms such that cells become resistant to oxidative stress (21,74).…”

“…In this way, the interaction between PNDF and TrKC receptors, which are receptors for the entry of T. cruzi into neural, glial, and epithelial cells, was recently demonstrated (73,74). This function is independent of sialic acid, which was demonstrated through the use of sialic acid mutant CHO cells and by the ability of the parasite to trigger the Akt response in the host cell cytosol, where there is no sialic acid available to the parasite, upregulating prosurvival mechanisms such that cells become resistant to oxidative stress (21,74). Therefore, TSs are part of the mechanism of survival in host cells, which facilitates the persistence of the parasite in infected tissues.…”