Isolation of two Locust protein targets of a protein tyrosine phosphatase from Metarhizium anisopliae strain CQMa102

In entomopathogenic fungi, secretory protein phosphatases might function in the utilization of phosphoproteins from the environment. But if secreted into the host, secretory protein phosphatases might play a role in pathogenesis by dephosphorylation of host phosphoproteins. Our group purified a novel phosphatase from entomopathogenic fungi, Metarhizium anisopliae. The substrate specificity and inhibitor sensitivity indicate that the phosphatase is a protein tyrosine phosphatase (PTPase). In order to analyze the targets of the PTPase in Locusta migratoria hemolymph, two-dimensional electrophoresis and mass spectrometry were used. The results indicated that the PTPase could specifically dephosphorylate two phosphoproteins from L. migratoria hemolymph. One phosphoprotein was identified as trans-Golgi p230. Previous studies have shown that trans-Golgi p230 participates in vesicular transport of functional proteins from the distal Golgi compartment. trans-Golgi p230 can be inactivated by dephosphorylation, which implies that M. anisopliae could interfere with the correct transportation of functional proteins by secreting extracellular PTPase into the hemolymph. There are some secretion proteins, such as transferrin, have been thought to participate in the insect innate immune against microbial infection, therefor M. anisopliae could interfere with immune defenses of L. migratoria by secreting extracellular PTPase into the hemolymph.