Serine protease inhibitors of the whirling disease parasite Myxobolus cerebralis (Cnidaria, Myxozoa): Expression profiling and functional predictions

Abstract

Here, we studied the expression pattern and putative function of four, previously identified serine protease inhibitors (serpins) of Myxobolus cerebralis, a pathogenic myxozoan species (Cnidaria: Myxozoa) causing whirling disease of salmonid fishes. The relative expression profiles of serpins were determined at different developmental stages both in fish and in annelid hosts using serpin-specific qPCR assays. The expression of serpin Mc-S1 was similar throughout the life cycle, whereas a significant decrease was detected in the relative expression of Mc-S3 and Mc-S5 during the development in fish, and then in the sporogonic stage in the worm host. A decreasing tendency could also be observed in the expression of Mc-S4 in fish, which was, however, upregulated in the worm host. For the first time, we predicted the function of M. cerebralis serpins by the use of several bioinformatics-based applications. Mc-S1 is putatively a chymotrypsin-like inhibitor that locates extracellularly and is capable of heparin binding. The other three serpins are caspase-like inhibitors, and they are probably involved in protease and cell degradation processes during the early stage of fish invasion.

The cnidarian parasite Ceratonova shasta utilizes inherited and recruited venom-like compounds during infection

“…Transcript 1 was heavily expressed at 1 dpe in the gills, and less at 7, 14 and 21 dpe in the intestines, whereas Transcript 2 was not expressed until 14 dpe. Asynchronous expression of protease inhibitors was likewise observed in M. cerebralis infections in Rainbow trout ( Eszterbauer et al, 2021 ). Like these proteins in M. cerebralis , Kunitz-type protease inhibitors in C. shasta may have several roles in evading host immunity.…”

The highly repetitive genome of Myxobolus sp., a myxozoan parasite of fathead minnows

“…In one such example of gene family expansion, serpins (serine proteases) play an important role in parasitic organisms, like defense against host proteases in Schistosoma mansoni and acting as immunomodulators and inhibit host immune responses in nematodes (Maizels et al, 2001; Valdivieso et al, 2015). Recently, a study analyzed the expression-profiles of M. cerebralis serpins and proposed that they represent good targets for inactivating the parasite at an early stage in the fish host (Eszterbauer et al, 2021). We found a group of M. rasmusseni proteins that clustered together with serpins 3, 4, and 5 from M. cerebralis.…”