Protoplast plasma membrane glycoproteins in two species of entomophthoralean fungi

The entomophthoralean fungi Entomophaga maimaiga and E. aulicae show host preferential infection in lepidopterous insects. These fungi grow as protoplasts within the haemocoel of the infected insect. We investigated differences in protoplast plasma membrane glycoproteins. The plasma membrane proteins from E. maimaiga and E. aulicae were isolated and assessed for enrichment based on H+-translocating ATPases which show membrane specific pH optima and specific inhibition sensitivities. Of the glycoproteins tested for, major differences in the pattern, type and magnitude of mannose glycosylation were observed in plasma membrane proteins from the two fungi. E. maimaiga plasma membrane proteins showed greater levels of glycosylation with mannose in relative comparison to plasma membrane proteins isolated from E. aulicae. In contrast to the differences observed with mannose glycosylation, both fungi showed a single molecular mass protein that was glycosylated with sialic acid as well as with galactose β(1–4) linked to N-acetyl-d-glucosamine. Addition of tunicamycin to culture media reduced the level of mannose glycosylation of plasma membrane proteins. The results are discussed with reference to alteration of plasma membrane glycoproteins aiding in avoidance of insect immune responses.