Trypanosome trans-sialidase targets TrkA tyrosine kinase receptor and induces receptor internalization and activation

Trypanosome trans-sialidase (TS) is a sialic acid-transferring enzyme that hydrolyzes a2,3-linked sialic acids and transfers them to acceptor molecules. Here we show that a highly purified recombinant TS derived from T. cruzi parasites targets TrkA receptors on TrkA-expressing PC12 cells and colocalizes with TrkA internalization and phosphorylation (pTrkA). Maackia amurensis lectin II (MAL-II) and Sambucus nigra lectin (SNA) block TS binding to TrkA-PC12 cells in a dose-dependent manner with subsequent inhibition of TS colocalization with pTrkA. Cells treated with lectins alone do not express pTrkA. The catalytically inactive mutant TSAAsp98-Glu also binds to TrkA-expressing cells, but is unable to induce pTrkA. TrkA-PC12 cells treated with a purified recombinant a2,3-neuraminidase (Streptococcus pneumoniae) express pTrkA. Wild-type TS but not the mutant TSΔAsp98-Glu promotes neurite outgrowth in TrkA-expressing PC12 cells. In contrast, these effects are not observed in TrkA deficient PC12 n n r 5 cells but are reestablished in PC12 n n r 5 cells stably transfected with TrkA and are significantly blocked by inhibitors of tyrosine kinase (K-252a) and MAP/MEK protein kinase (PD98059). Together these observations suggest for the first time that hydrolysis of sialyl a2,3-linked (3-galactosyl residues of TrkA receptors plays an important role in TrkA receptor activation, sufficient to promote cell differentiation (neurite outgrowth) independent of nerve growth factor.