Proteomic Analysis of the Parasitic Cnidarian Ceratonova shasta (Cnidaria: Myxozoa) Reveals Diverse Roles of Actin in Motility and Spore Formation

Abstract

Myxozoans are widely distributed aquatic obligate endoparasites that were recently recognized as belonging within the phylum Cnidaria. They have complex life cycles with waterborne transmission stages: resistant, infectious spores that are unique to myxozoans. However, little is known about the processes that give rise to these transmission stages. To understand the molecular underpinnings of spore formation, we conducted proteomics on Ceratonova shasta, a highly pathogenic myxozoan that causes severe mortalities in wild and hatchery-reared salmonid fishes. We compared proteomic profiles between developmental stages from inside the fish host, and the mature myxospore, which is released into the water where it drifts passively, ready to infect the next host. We found that C. shasta contains 2,123 proteins; representing the first proteomic catalog of a myxozoan myxospore. Analysis of proteins differentially expressed between developing and mature spore stages uncovered processes that are active during spore formation. Our data highlight dynamic changes in the actin cytoskeleton, which provides myxozoan developmental stages with mobility through lamellipodia and filopodia, whereas in the mature myxospore the actin network supports F-actin stabilization that reinforces the transmission stage. These findings provide molecular insight into the myxozoan life cycle stages and, particularly, into the process of sporogenesis.

Proteases as Therapeutic Targets Against the Parasitic Cnidarian Ceratonova shasta: Characterization of Molecules Key to Parasite Virulence In Salmonid Hosts

“…C. shasta aminopeptidase-N was expressed mostly at latter time points in both genotypes, and was coincident with the onset of spore production (Figure 3). These expression results align with the proteomic data of the type IIR nematocyst, where the aminopeptidase-N protein was found to be of special significance (Piriatinskiy et al, 2017;Brekhman et al, 2021). These findings and the role of aminopeptidases in other parasite groups suggest that this zinc-metalloprotease could be involved in the formation of nematocysts during C. shasta sporogenesis, more specifically in the pressurization of nematocysts.…”

“…This protease is significantly upregulated only in the virulent genotype IIR, beginning early in the infection and with a peak of expression at 15 dpe, when IIR infection is established in the intestine and proliferation, sporogenesis and systemic infection is increasing (Figure 3). C. shasta aspartic protease is present in proteomic data from developmental stages but nearly absent in myxospore proteomes (Brekhman et al, 2021). We assume that C. shasta cathepsin D could contribute to the rapid proliferation and virulence of this genotype by causing the destruction of the intestinal extracellular matrix in order to satisfy the high demand for nutrients by the developmental stages.…”

“…Genotype IIR shows higher expression of stefin, with a particularly high fold change at 15 dpe, probably to regulate parasite cysteine proteases used for rapid proliferation and spore formation (Figure 3). In fact, this stefin is present in IIR C. shasta proteomic data from ascites but absent from mature myxospores (Brekhman et al, 2021). Similarly, other parasite stefins are expressed in developmental stages or trophozoites during encystation, when large volumes of intracellular components are required and protection from cysteine protease activities is needed to avoid intracellular damage (Lee et al, 2013).…”

Identification of in vivo induced antigens of the malacosporean parasite Tetracapsuloides bryosalmonae (Cnidaria) using in vivo induced antigen technology

“…Capping protein is an alpha/beta heterodimer and it is an important protein in eukaryotes for actin cytoskeleton development ( Hart et al., 1997 ). The role of F-actin has been confirmed in motility and spore formation in C. shasta ( Brekhman et al., 2021 ). In light of these reports, and our present study, Rho family genes in T. bryosalmonae could play important roles and interact with antibodies of infected fish during the development of the disease.…”

A myxozoan genome reveals mosaic evolution in a parasitic cnidarian

“…Myxozoans require motile stages both to avoid host immune responses [ 82 ] and to reach target tissues. In Ceratonova shasta and Ceratomyxa puntazzi , actin has an important role in stage motility [ 83 , 84 ], and our finding that here M. honghuensis is enriched in lineage-specific regulators of the actin cytoskeleton (Additional file 1 : Table S17), suggests that actin may be important for success of diverse myxozoan taxa.…”