The claudin-like apicomplexan microneme protein is required for gliding motility and infectivity of Plasmodium sporozoites

Abstract

Invasion of host cells by apicomplexan parasites such as Toxoplasma and Plasmodium spp requires the sequential secretion of the parasite apical organelles, the micronemes and the rhoptries. The claudin-like apicomplexan microneme protein (CLAMP) is a conserved protein that plays an essential role during invasion by Toxoplasma gondii tachyzoites and in Plasmodium falciparum asexual blood stages. CLAMP is also expressed in Plasmodium sporozoites, the mosquito-transmitted forms of the malaria parasite, but its role in this stage is still unknown. CLAMP is essential for Plasmodium blood stage growth and is refractory to conventional gene deletion. To circumvent this obstacle and study the function of CLAMP in sporozoites, we used a conditional genome editing strategy based on the dimerisable Cre recombinase in the rodent malaria model parasite P. berghei. We successfully deleted clamp gene in P. berghei transmission stages and analyzed the functional consequences on sporozoite infectivity. In mosquitoes, sporozoite development and egress from oocysts was not affected in conditional mutants. However, invasion of the mosquito salivary glands was dramatically reduced upon deletion of clamp gene. In addition, CLAMP-deficient sporozoites were impaired in cell traversal and productive invasion of mammalian hepatocytes. This severe phenotype was associated with major defects in gliding motility and with reduced shedding of the sporozoite adhesin TRAP. Expansion microscopy revealed partial colocalization of CLAMP and TRAP in a subset of micronemes, and a distinct accumulation of CLAMP at the apical tip of sporozoites. Collectively, these results demonstrate that CLAMP is essential across invasive stages of the malaria parasite, and support a role of the protein upstream of host cell invasion, possibly by regulating the secretion or function of adhesins in Plasmodium sporozoites.

Whole‐genome CRISPR screens to understand Apicomplexan–host interactions

“…This enabled the first genome‐wide CRISPR/Cas9 loss‐of‐function screen in Toxoplasma , identifying fitness‐conferring genes critical for invasion of the host cell, including clamp (claudin‐like Apicomplexan microneme protein) (Table 1). Phenotypic validation studies confirmed CLAMP's importance in Toxoplasma invasion and the P. falciparum lytic cycle as well as in sporozoites (Loubens et al., 2023).…”

Microtubule inner proteins ofPlasmodiumare essential for transmission of malaria parasites

“…Investigating the three mutants we found that all formed similar numbers of sporozoites in oocysts and that all could colonize the salivary glands to similar levels (Figure 2C). Sporozoites move at high speeds and thus deletion of genes often affects their gliding motility (43,(46)(47)(48). To investigate gliding activity, we allowed salivary gland derived sporozoites to settle on a glass substrate and imaged their movement.…”

Malaria Elimination in Africa: Rethinking Strategies for Plasmodium vivax and Lessons from Botswana

“…An infection is initiated when a female Anopheline mosquito infected with the parasite inoculates an estimated 15–123 sporozoites under the skin of an individual while probing for a blood vessel to take a meal [ 16 , 17 , 18 , 19 , 20 ]. While under the skin, the sporozoites get activated based on the environmental milieu, express proteins required for gliding motility and cell traversal and travel through the blood to the liver using the sinusoids as entry points to hepatocytes [ 21 , 22 , 23 , 24 ]. The sinusoids are lined with resident macrophages, the Kupffer cells that aid in the transmigration of the sporozoites via gliding motility [ 25 ] through the sinusoids to reach hepatocytes [ 26 , 27 ].…”