title: The Heme Transport Capacity of LHR1 Determines the Extent of Virulence in Leishmania amazonensis.
abstract: Leishmania spp. are trypanosomatid parasites that replicate intracellularly in macrophages, causing serious human morbidity and mortality throughout the world. Trypanosomatid protozoa cannot synthesize heme, so must acquire this essential cofactor from their environment. Earlier studies identified LHR1 as a Leishmania amazonensis transmembrane protein that mediates heme uptake. Null mutants of LHR1 are not viable and single knockout strains have reduced virulence, but very little is known about the properties of LHR1 directly associated with heme transport. Here, we use functional assays in Saccharomyces cerevisiae to show that specific tyrosine residues within the first three predicted transmembrane domains of LHR1 are required for efficient heme uptake. These tyrosines are unique to LHR1, consistent with the low similarity between LHR1 and its corresponding homologs in C. elegans and human. Substitution of these tyrosines in LHR1 resulted in varying degrees of heme transport inhibition, phenotypes that closely mirrored the impaired ability of L. amazonensis to replicate as intracellular amastigotes in macrophages and generate cutaneous lesions in mice. Taken together, our results imply that the mechanism for heme transport by LHR1 is distinctive and may have adapted to secure heme, a limiting cofactor, inside the host. Since LHR1 is significantly divergent from the human heme transporter HRG1, our findings lay the groundwork for selective targeting of LHR1 by small molecule antagonists.
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Renberg
authors.affiliation: Department of Animal and Avian Sciences, University of Maryland, College Park, Maryland, United States of America.
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Yuan
authors.affiliation: Department of Animal and Avian Sciences, University of Maryland, College Park, Maryland, United States of America.
authors.forename: Tamika K
authors.initials: TK
authors.lastname: Samuel
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America.
authors.forename: Danilo C
authors.initials: DC
authors.lastname: Miguel
authors.affiliation: Department of Animal and Avian Sciences, University of Maryland, College Park, Maryland, United States of America.
authors.forename: Iqbal
authors.initials: I
authors.lastname: Hamza
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America.
authors.forename: Norma W
authors.initials: NW
authors.lastname: Andrews
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America; PathSensors, Inc., Baltimore, Maryland, United States of America.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Flannery
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D017173:Caenorhabditis elegans / Q000235:genetics; D005260:Female; D017930:Genes, Reporter; D006418:Heme / Q000378:metabolism*; D006801:Humans; D007894:Leishmania mexicana / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D008264:Macrophages / Q000469:parasitology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D016415:Sequence Alignment; D014443:Tyrosine; D014774:Virulence
chemical_list: D008565:Membrane Proteins; D015800:Protozoan Proteins; D014443:Tyrosine; D006418:Heme