title: Regulation of intracellular heme trafficking revealed by subcellular reporters.
abstract: Heme is an essential prosthetic group in proteins that reside in virtually every subcellular compartment performing diverse biological functions. Irrespective of whether heme is synthesized in the mitochondria or imported from the environment, this hydrophobic and potentially toxic metalloporphyrin has to be trafficked across membrane barriers, a concept heretofore poorly understood. Here we show, using subcellular-targeted, genetically encoded hemoprotein peroxidase reporters, that both extracellular and endogenous heme contribute to cellular labile heme and that extracellular heme can be transported and used in toto by hemoproteins in all six subcellular compartments examined. The reporters are robust, show large signal-to-background ratio, and provide sufficient range to detect changes in intracellular labile heme. Restoration of reporter activity by heme is organelle-specific, with the Golgi and endoplasmic reticulum being important sites for both exogenous and endogenous heme trafficking. Expression of peroxidase reporters in Caenorhabditis elegans shows that environmental heme influences labile heme in a tissue-dependent manner; reporter activity in the intestine shows a linear increase compared with muscle or hypodermis, with the lowest heme threshold in neurons. Our results demonstrate that the trafficking pathways for exogenous and endogenous heme are distinct, with intrinsic preference for specific subcellular compartments. We anticipate our results will serve as a heuristic paradigm for more sophisticated studies on heme trafficking in cellular and whole-animal models.
authors.affiliation: Department of Animal & Avian Sciences, University of Maryland, College Park, MD 20742; Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD 20742;
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Yuan
authors.affiliation: Department of Animal & Avian Sciences, University of Maryland, College Park, MD 20742; Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD 20742;
authors.forename: Nicole
authors.initials: N
authors.lastname: Rietzschel
authors.affiliation: Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 9HN, United Kingdom;
authors.forename: Hanna
authors.identifier: 0000-0001-6941-4808
authors.initials: H
authors.lastname: Kwon
authors.affiliation: Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-590, Brazil;
authors.forename: Ana Beatriz
authors.initials: AB
authors.lastname: Walter Nuno
authors.affiliation: School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332; Parker H. Petit Institute of Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, GA 30332;
authors.forename: David A
authors.initials: DA
authors.lastname: Hanna
authors.affiliation: Division of Hematology, University of Utah School of Medicine, Salt Lake City, UT 84132;
authors.forename: John D
authors.initials: JD
authors.lastname: Phillips
authors.affiliation: Department of Chemistry, University of Leicester, Leicester LE1 7RH, United Kingdom.
authors.forename: Emma L
authors.initials: EL
authors.lastname: Raven
authors.affiliation: School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332; Parker H. Petit Institute of Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, GA 30332;
authors.forename: Amit R
authors.initials: AR
authors.lastname: Reddi
authors.affiliation: Department of Animal & Avian Sciences, University of Maryland, College Park, MD 20742; Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD 20742; hamza@umd.edu.
authors.forename: Iqbal
authors.initials: I
authors.lastname: Hamza
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001692:Biological Transport; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004705:Endocytosis; D057809:HEK293 Cells; D006418:Heme / Q000737:chemistry / Q000378:metabolism*; D006420:Hemeproteins / Q000378:metabolism*; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism*; D018613:Microscopy, Confocal; D015388:Organelles / Q000378:metabolism; D009195:Peroxidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D006420:Hemeproteins; D006418:Heme; D009195:Peroxidase
keywords: heme; iron; subcellular; tetrapyrroles; trafficking