Differentially expressed Leishmania major gp63 genes encode cell surface leishmanolysin with distinct signals for glycosylphosphatidylinositol attachment.

The Leishmania cell surface metalloproteinase, leishmanolysin or GP63, is expressed in all stages of Leishmania major. Initial studies reported that in L. major the gp63 genes were arranged as five homologous, tandemly repeated genes (gp63 genes 1-5) and a sixth, less conserved gp63 gene located 8 kb downstream of gp63 gene 5. This study compared the sequences of L. major gp63 gene 1 and gp63 gene 6 and identified a seventh L. major gp63 gene located downstream from gp63 gene 6. The L. major gp63 genes exhibited stage-specific differences in their expression: gp63 genes 1-5 were expressed in promastigotes only, gp63 gene 6 was expressed in promastigotes and amastigotes, while gp63 gene 7 was expressed predominantly in stationary phase promastigotes and in amastigotes. Analysis of the predicted protein sequence of gp63 gene 6 (GP63-6) and gp63 gene 1 (GP63-1) showed that these two proteins were homologous in terms of overall predicted domain structure. L. major GP63-1 has been reported to contain a glycosylphosphatidylinositol (GPI) membrane anchor while sequence analysis predicted that GP63-6 contained a different hydrophobic C-terminus that may act as a transmembrane region. Transfection studies using L. major gp63 gene 1 and gp63 gene 6 expressed in L. donovani promastigotes showed that GP63-6 was expressed at the cell surface and that the distinct GP63-6 C-terminus was capable of mediating GPI anchor attachment.