Role for copper in the cellular and regulatory effects of heme-hemopexin.
Hemopexin (HPX) binds heme tightly, thus protecting cells from heme toxicity during hemolysis, trauma and ischemia-reperfusion injury. Heme uptake via endocytosis of heme-HPX followed by heme catabolism by heme oxygenase-1 (HMOX1) raises regulatory iron pools, thus linking heme metabolism with that of iron. Normal iron homeostasis requires copper-replete cells. When heme-HPX induces HMOX1, the copper-storing metallothioneins (MTs) are also induced whereas the copper-responsive copper chaperone that delivers copper to Cu, Zn superoxide dismutase, CCS1, is decreased; both are known responses when cellular copper levels rise. Endocytosis of heme-HPX is needed to regulate CCS1 since the signaling ligand cobalt-protoporphyrin (CoPP)-HPX, which does not induce HMOX1 but does co-localize with heme-HPX in endosomes, also decreased CCS1. These observations support that heme-HPX mobilizes copper in cells. The regulation of both hmox1 and mt1 is prevented by the copper-chelator, bathocuproinedisulfonate (BCDS), but not uptake of heme-AlexaFluor-labeled HPX into endosomes. Supporting a role for copper in HMOX1 regulation by heme-HPX, nutritional copper deficiency generated by tetraethylene pentamine or 232 tetraamine prevented HMOX1 induction. Using conditions that mimic maturing endosomes, we found that copper prevents rebinding of heme to apo-HPX. A model is presented in which copper endocytosis together with that of heme-HPX provides a means to facilitate heme export from HPX in the maturing endosomes: heme is needed for hmox1 transcription, while cytosolic copper and CCS1 provide a link for the known simultaneous regulation of hmox1 and mt1 by heme-HPX.
Smith
Ann
A
Division of Molecular Biology & Biochemistry, School of Biological Sciences, University of Missouri-K.C., 5007 Rockhill Road, Kansas City, MO 64110, USA. smithan@umkc.edu
Rish
Kimberly R
KR
Lovelace
Rachel
R
Hackney
Jennifer F
JF
Helston
Rachel M
RM
D000818:Animals; D045744:Cell Line, Tumor; D003300:Copper / Q000737:chemistry / Q000172:deficiency / Q000502:physiology*; D004705:Endocytosis / Q000187:drug effects; D011992:Endosomes / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005029:Ethylenediamines / Q000737:chemistry; D006418:Heme / Q000737:chemistry / Q000494:pharmacology*; D051547:Heme Oxygenase-1 / Q000378:metabolism*; D006466:Hemopexin / Q000737:chemistry / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000378:metabolism*; D008668:Metallothionein / Q000378:metabolism; D051379:Mice; D018832:Molecular Chaperones / Q000378:metabolism
C491962:Ccs protein, mouse; D005029:Ethylenediamines; D008565:Membrane Proteins; D018832:Molecular Chaperones; D006418:Heme; D003300:Copper; D006466:Hemopexin; D008668:Metallothionein; D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse; C034269:tetraethylenepentamine