Investigation of the molecular mechanism of RON4 in Plasmodium berghei sporozoite infection of mammalian hosts

Malaria parasites develop inside mosquitoes and become sporozoites, the form that infects mammals. Sporozoites actively invade the salivary glands of mosquitoes, are implanted into the skin of mammals as they suck blood, reach the liver through the bloodstream, pass through the sinusoidal wall of the liver, and infect hepatocytes.  In the previous year, using sporozoite stage-specific RON4 expression-suppressed protozoa, it was clarified that RON4 is involved in the motility of sporozoites, the entry into salivary glands, the passage of cells necessary for reaching the liver parenchyma, and the parasitism of hepatocytes. bottom. Next, in order to clarify whether protozoa at these stages express RON4, the expression pattern of RON4 protein was observed using protozoa fused with mCherry to the C-terminus of RON4 and anti-RON4 antibody. In midgut sporozoites, mCherry fluorescence was detected at the tip of the worm body, and in salivary gland sporozoites, fluorescence was also observed at the same position. One hour after inoculation into cultured hepatocyte HepG2, RON4 was observed in more than half of the parasites, but 6 hours after inoculation, more than 80% of the parasites were below the detection limit, and RON4 was completely absent after 24 hours. After that, RON4 signals were observed at the tip of merozoites 48 to 72 hours later, as they differentiated and matured into erythrocyte-infectious merozoites (merozoites) in hepatocytes. Suppression of RON4 expression significantly suppressed the motility of sporozoites. To investigate whether RON4 is secreted and functions during exercise, sporozoites were allowed to glide on a glass slide without permeabilization. Fluorescent staining was performed using an anti-RON4 antibody. As a result, RON4 signals were observed outside the sporozoite body. This suggests that sporozoites secrete RON4 during gliding movement.

Project details

Basic Science

Apr 2020 — Mar 2023

$36,954

Japan