CD9 is a widely expressed cell surface molecule that belongs to the tetraspanin superfamily of proteins. The tetraspanins CD9, KAI-1/CD82, and CD63 are involved in metastasis suppression, an effect that may be related to their association with beta1 integrins. Knockout mice lacking CD9 were created to evaluate the physiological importance of CD9. CD9-/- females displayed a severe reduction of fertility. Oocytes were ovulated but were not successfully fertilized because sperm did not fuse with the oocytes from CD9-/- females. Thus, CD9 appears to be essential for sperm-egg fusion, a process involving the CD9-associated integrin alpha6beta1.
Plasmodium sporozoites are transmitted through the bite of infected mosquitoes and first invade the liver of the mammalian host, as an obligatory step of the life cycle of the malaria parasite. Within hepatocytes, Plasmodium sporozoites reside in a membrane-bound vacuole, where they differentiate into exoerythrocytic forms and merozoites that subsequently infect erythrocytes and cause the malaria disease. Plasmodium sporozoite targeting to the liver is mediated by the specific binding of major sporozoite surface proteins, the circumsporozoite protein and the thrombospondin-related anonymous protein, to glycosaminoglycans on the hepatocyte surface. Still, the molecular mechanisms underlying sporozoite entry and differentiation within hepatocytes are largely unknown. Here we show that the tetraspanin CD81, a putative receptor for hepatitis C virus, is required on hepatocytes for human Plasmodium falciparum and rodent Plasmodium yoelii sporozoite infectivity. P. yoelii sporozoites fail to infect CD81-deficient mouse hepatocytes, in vivo and in vitro, and antibodies against mouse and human CD81 inhibit in vitro the hepatic development of P. yoelii and P. falciparum, respectively. We further demonstrate that the requirement for CD81 is linked to sporozoite entry into hepatocytes by formation of a parasitophorous vacuole, which is essential for parasite differentiation into exoerythrocytic forms.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.