CLONING OF THE GP63 SURFACE PROTEASE OF LEISHMANIA-INFANTUM - DIFFERENTIAL POSTTRANSLATIONAL MODIFICATIONS CORRELATED WITH DIFFERENT INFECTIVE FORMS

The Leishmania cell surface virulence factor gp63 is a protease family that plays an important role in the survival of the parasite protozoo n into the host macrophages. We have cloned and characterised the gp63 gene from L. infantum. The sequence analysis of the gene indicates th e existence of a high degree of conservation with the other old world species L. major and L. donovani. The similarity is lower with new wor ld species with the exception of L. chagasi which shows a strikingly h igh percentage of identity (99-100%). In L. infantum the gp63 gene exp resses two polypeptides of 58 and 60 kDa, respectively, which show a s imilar proteolytic activity. The 60 kDa polypeptide is expressed durin g the whole life cycle of the promastigote form of the parasite with a moderate increase at the stationary phase of growth while the 58 kDa product, although slightly present in the logarithmic phase, notable i ncreases its expression during the highly infectious stationary phase. RNA analysis showed that the presence in L. chagasi of these two poly peptides correlates with two RNA molecules and with the degree of para site infectivity, whereas in the case of L. infantum a single 3 kb mes senger RNA is detected through the whole promastigote life cycle. Our data indicate that in L. infantum, the differences in gene expression of the gp63 protease family according to parasite phase of growth seem to be due to a differential pattern of glycosilation of the polypepti des which correlates with the different infective forms of the promast igote form of the parasite.