The effect of tunicamycin on Leishmania brasiliensis. Glycosylation and the cell surface components

Relationships between cell surface protease and acid phosphatase activities of Leishmania promastigote

A correlation between the ratio of the cell surface protease activity to phosphatase activity and the complexity of the pattern of cell surface exposed polypeptides of Leishmania promastigotes was demonstrated for various strains grown under similar conditions. The ratio of the cell surface protease activity to acid phosphatase activity was high for L. major and L.b. panamensis and it correlates with the expression of a single polypeptide of 63 KDa on their cell surface. Intermediate and lower ratios of these enzymatic activities relate with more complex radio-iodinated patterns: two main bands in L.b. guyanensis (70 and 58 KDa) and L.b. braziliensis (72 and 60 KDa) and three main bands 65, 50, 27 KDa in all L.m. mexicana strains tested. Evidence is presented that the acid phosphatase located on the L.m. mexicana cell surface is not an artifact due to a secondary absorption of the secreted acid phosphatase from the culture medium. These results confirm the Leishmania antigen cell surface heterogeneity. The implications on the biology of Leishmania and the clinical manifestation of leishmaniasis are discussed.

Antigenic analysis of Leishmania isolates from Tachira state, Venezuela

Studies of cutaneous leishmaniasis in 3 endemic foci in Tachira state, western Venezuela have revealed sympatric populations of parasites causing both cutaneous and mucocutaneous disease. Immunological techniques and measurement of protease/acid phosphatase activities have been used to detect species-specific parasite antigens from 3 isolates from Tachira. Identified antigens of particular interest had molecular masses of 100, 82, 66, 50 and 27 kDa, but there was a high degree of heterogeneity between the antigens of the Tachira isolates and other Venezuelan strains of Leishmania braziliensis and L. mexicana. This heterogeneity has implications concerning the selection of antigens for use in serodiagnosis of leishmaniasis.

The effect of tunicamycin on the protease activity of GP63 from Leishmania major

The protease activity of gp63 from L. major was studied in relation to tunicamycin induced N-deglycosylation. It was found that after tunicamycin treatment, a N-deglycosylated product of gp63 with protease activity is present at the cell surface of Leishmania promastigote.

Effects of trifluoroacetic acid, a halothane metabolite, on C6 glioma cells

Effects of trifluoroacetic acid (TFA) on cell growth, DNA, glycoprotein, and dolichol-linked oligosaccharides synthesis and ribonucleotide triphosphate concentrations were examined in exponentially growing C6 murine glioma cells. One day of treatment with TFA caused a slight concentration-dependent enhancement of cell growth and [3H]thymidine incorporation. Exposure for 1 or 5 d to TFA (0.5-7.0 mM) elevated the [3H]leucine incorporation in a dose- and time-dependent manner. The results suggested that TFA stimulated cell growth and enhanced protein synthesis. TFA also affected [3H]mannose incorporation into glycoproteins and dolichol-linked oligosaccharides in a dose-dependent fashion. In addition, it was found that TFA accelerated lectin-induced cell agglutination. These data suggest that TFA, the principle halothane metabolite, alters plasmalemmal glycoprotein synthesis. These findings should form a basis for further understanding on the mechanism underlying halothane-associated neurotoxicity.

Biochemical evidence of the antigenic cell surface heterogeneity of Leishmania mexicana

In the present study, an enzymatical and structural analysis of Leishmania mexicana cell-surface components was carried out, demonstrating that protease and acid phosphatase activities were present at the L. mexicana cell surface. These findings correlate with the expression of the main components detected on the surface of L. mexicana promastigotes: the 50-kDa component is responsible for the acid phosphatase activity, whereas glycoprotein 65 (gp65) was characterized as the structural polypeptide of the surface protease. Furthermore, the 50- and 65-kDa antigens were found to be structurally different, inasmuch as no homology was observed in their peptide digestion profiles. The results presented in this communication confirm heterogeneity in the expression of the surface components of L. mexicana promastigotes at both the structural and the biochemical level.

The heterogeneity of Leishmania cell-surface antigens

A comparative study of the radioiodinated promastigote cell-surface antigens of Leishmania mexicana and L. major was carried out under reduced and nonreduced conditions by means of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by autoradiography. Under reduced conditions, the cell surface of L. mexicana promastigotes showed three iodinated polypeptides with molecular weights of 65,000, 50,000 and 27,000 daltons, whereas L. major promastigotes displayed a single polypeptide of 63,000 daltons. Under nonreduced conditions, the radioiodinated cell-surface component of L. major shifted to a mol.wt. of 51,000 daltons, whereas only one of the three components of L. mexicana (mol.wt., 65,000 daltons) underwent a large shift (to 59,000 daltons). The different immunochemical nature of the L. mexicana cell-surface antigens was demonstrated by using different anti-Leishmania sera. The rabbit anti-promastigote serum immunoprecipitated mainly the 50,000- and 27,000-dalton L. mexicana cell-surface polypeptides, whereas the rabbit anti-amastigote serum as well as a serum from a patient with cutaneous leishmaniasis immunoprecipitated almost exclusively the 65,000-dalton polypeptide. Immunoblot studies using a rabbit antibody against the L. major deglycosylated major surface antigen gp63 confirmed the differences in nature of the 65,000- and 50,000-dalton cell-surface antigens of L. mexicana. The results obtained are discussed in the light of the differences in antigenic cell-surface expression among Leishmania isolates and their consequences in the development of a differential diagnosis of leishmaniasis.