title: Invasion of hepatocytes by Plasmodium sporozoites requires cGMP-dependent protein kinase and calcium dependent protein kinase 4.
abstract: Invasion of hepatocytes by sporozoites is essential for Plasmodium to initiate infection of the mammalian host. The parasite's subsequent intracellular differentiation in the liver is the first developmental step of its mammalian cycle. Despite their biological significance, surprisingly little is known of the signalling pathways required for sporozoite invasion. We report that sporozoite invasion of hepatocytes requires signalling through two second-messengers - cGMP mediated by the parasite's cGMP-dependent protein kinase (PKG), and Ca2+, mediated by the parasite's calcium-dependent protein kinase 4 (CDPK4). Sporozoites expressing a mutated form of Plasmodium berghei PKG or carrying a deletion of the CDPK4 gene are defective in invasion of hepatocytes. Using specific and potent inhibitors of Plasmodium PKG and CDPK4, we demonstrate that PKG and CDPK4 are required for sporozoite motility, and that PKG regulates the secretion of TRAP, an adhesin that is essential for motility. Chemical inhibition of PKG decreases parasite egress from hepatocytes by inhibiting either the formation or release of merosomes. In contrast, genetic inhibition of CDPK4 does not significantly decrease the number of merosomes. By revealing the requirement for PKG and CDPK4 in Plasmodium sporozoite invasion, our work enables a better understanding of kinase pathways that act in different Plasmodium stages.
authors.affiliation: Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers - New Jersey Medical School, Newark, NJ, USA.
authors.forename: K
authors.initials: K
authors.lastname: Govindasamy
authors.affiliation: Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers - New Jersey Medical School, Newark, NJ, USA.
authors.forename: S
authors.initials: S
authors.lastname: Jebiwott
authors.affiliation: Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers - New Jersey Medical School, Newark, NJ, USA.
authors.forename: D K
authors.initials: DK
authors.lastname: Jaijyan
authors.affiliation: Department of Biostatistics, Rutgers - School of Public Health, Newark, NJ, USA.
authors.forename: A
authors.initials: A
authors.lastname: Davidow
authors.affiliation: Division of Allergy and Infectious Diseases, Center for Emerging and Re-emerging Infectious Diseases, University of Washington, Seattle, WA, USA.
authors.forename: K K
authors.initials: KK
authors.lastname: Ojo
authors.affiliation: Division of Allergy and Infectious Diseases, Center for Emerging and Re-emerging Infectious Diseases, University of Washington, Seattle, WA, USA.
authors.forename: W C
authors.initials: WC
authors.lastname: Van Voorhis
authors.affiliation: CNRS UMR5235 -Université Montpellier 2, 34095, Montpellier, France.|University of Geneva, Faculty of Medicine, Department of Microbiology and Molecular Medicine, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Brochet
authors.affiliation: Wellcome Trust Sanger Institute, Malaria Programme, CB10 1SA, Hinxton, UK.
authors.forename: O
authors.initials: O
authors.lastname: Billker
authors.affiliation: Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers - New Jersey Medical School, Newark, NJ, USA. bhanotpu@njms.rutgers.edu.
authors.forename: P
authors.initials: P
authors.lastname: Bhanot
mesh_terms: D000818:Animals; D000852:Anopheles / Q000469:parasitology; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism*; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000378:metabolism / Q000469:parasitology*; D006801:Humans; D010962:Plasmodium berghei / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D010963:Plasmodium falciparum / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D015800:Protozoan Proteins / Q000378:metabolism; D015398:Signal Transduction; D034101:Sporozoites / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases
chemical_list: D002118:Calcium; D002135:Calcium-Binding Proteins; D006152:Cyclic GMP; D017869:Cyclic GMP-Dependent Protein Kinases; D011494:Protein Kinases; D015800:Protozoan Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases