Essential role of membrane-attack protein in malarial transmission to mosquito host

Abstract

After ingestion of infected blood by a mosquito, malarial parasites are fertilized in the mosquito midgut and develop into motile ookinetes. These ookinetes invade epithelial cells by rupturing the cell membrane and migrate through the cytoplasm toward the basal lamina, on which they develop to oocysts. Here we report that a microneme protein with a membrane-attack complex and perforin (MACPF)-related domain, which we name membraneattack ookinete protein (MAOP), is produced in the ookinete stage and plays an essential role in midgut invasion by the ookinete. Ookinetes with the MAOP gene disrupted completely lost infectivity to the midgut. After ingestion of blood infected with the disrupted parasite, the midgut epithelium remained intact, making a clear contrast with the damaged midgut epithelium invaded by wild-type ookinetes. Electron microscopic analysis showed that the disruptant ookinetes migrate to the gut epithelium and attach to the cell surface at the apical tip, but are unable to enter the cytoplasm by rupturing the cell membrane. These results indicate that the MAOP molecule acts on the plasma membrane of the host-cell-like mammalian MACPF family proteins that create pores in the membrane of target cells. Another previously identified MACPF-related molecule is produced in the liver-infective sporozoite and has a crucial role in traversing the liver sinusoidal cell boundary. The present finding, thus, suggests that conserved mechanisms for membrane rupture involving MACPF-related proteins are used in different host invasive stages of the malarial parasite, playing a key role in breaching biological barriers of host organs.malaria ͉ ookinete ͉ host cell invasion ͉ membrane rupture ͉ membraneattack complex and perforin-related proteins M alaria is still the most important parasitic disease in the world, responsible for 300 million to 500 million cases of illness and 1.5 million to 2.7 million deaths annually. Because of the spread of chloroquine-resistant malaria parasites and insecticide-resistant mosquitoes, malaria is still a major public health problem.Malarial parasites are transmitted to humans by anopheline mosquitoes. After ingestion of infected blood by a mosquito, malarial parasites are fertilized in the mosquito midgut and develop into motile zygotes, called ookinetes. Ookinetes invade the midgut epithelial cell from the luminal surface by rupturing the cell membrane and move through the cytoplasm to the side of the basal lamina, sometimes penetrating additional epithelial cells laterally (1, 2). On the basal lamina, ookinetes transform to oocysts and finally develop to sporozoites, the mosquito salivary gland-invasive stage.During this midgut invasion, many ookinetes are killed by the insect's defense system, and the number of malarial parasites is greatly reduced (2-4). The midgut epithelium is, therefore, one of the most important biological barriers against malarial infection. To breach this barrier and migrate to the site of further development, ookinetes have the ability to traverse the ...

The development of malaria parasites in the mosquito midgut

“…Other microneme proteins assigned to midgut traversal of P . berghei ookinetes include SOAP, WARP and CelTOS (cell‐traversal protein for ookinetes and sporozoites) (Yuda et al ., 2001; Dessens et al ., 2003; Kadota et al ., 2004; Li et al ., 2004; Kariu et al ., 2006; Ecker et al ., 2007, 2008; Kaneko et al ., 2015; Wirth et al ., 2015) (Table 1). …”

Reductive genome evolution, host–symbiont co-speciation and uterine transmission of endosymbiotic bacteria in bat flies

“…The generic name honors Manfred Aschner, who first described the endosymbionts of nycteribiid bat flies (Aschner, 1931(Aschner, , 1946. The specific name is after a Japanese biologist Yasuo Chinzei, who significantly contributed to the biochemistry and molecular biology of blood-sucking insects (Yuda et al, 1996;Kadota et al, 2004).…”

Cellular and molecular interactions between the apicomplexan parasitesPlasmodiumandTheileriaand their host cells

“…In exiting the midgut, the ookinete traverses a number of midgut epithelial cells before reaching the basal lamina and rounding up to become an oocyst (Zieler & Dvorak, 2000). The process of cell transmigration is similar to that displayed by sporozoites in traversing hepatocytes, again requiring the action of perforin-like proteins (Ecker et al, 2007;Ishino et al, 2005;Kadota et al, 2004). In both processes, a prerequisite of parasite transmigration is secretion of the parasite protein CelTOS into the cytoplasm of the traversed cell (Kariu et al, 2006).…”

“…Activation of sporozoites is believed to occur by their contact with the intracellular environment of the hepatocyte and at least in part appears to be due to their exposure to intracellular concentrations of potassium (Kumar et al, 2007). To gain entry into a hepatocyte for traversal, sporozoites puncture the cell membrane using a perforin-like protein, spect2, or pplp1 (Ishino et al, 2005;Kadota et al, 2004). Sporozoite activation by cell traversal does not, however, appear to be essential, as genetically modified spect2-negative parasites, which were unable to traverse hepatocytes, can successfully infect hepatocytes in by , and the activation and suppression of host cell death are indicated by → and respectively.…”