Caveolae compartmentalization of heme oxygenase-1 in endothelial cells

FASEB J. 2004 Jul;18(10):1080-9. doi: 10.1096/fj.03-1391com.


The heme oxygenase (HO) and nitric oxide synthase (NOS) enzymes generate the gaseous signaling molecules carbon monoxide (CO) and nitric oxide, respectively. Constitutive NOSs localize to caveolae, and their activities are modulated by caveolin-1. Nothing is known of the localization of the inducible heme oxygenase-1 (HO-1) in plasma membrane caveolae. Thus, we examined the distribution and subcellular localization of HO-1, biliverdin reductase (BVR), and NADPH:cytochrome P450 reductase (NPR) in pulmonary artery endothelial cells. Each of these proteins localized in part to plasma membrane caveolae in endothelial cells. Inducers of HO-1 or overexpression of HO-1 increased the content of this protein in a detergent-resistant fraction containing caveolin-1. Inducible HO activity appeared in plasma membrane, cytosol, and isolated caveolae. In addition, caveolae contained endogenous BVR activity, supporting the same compartmentalization of both enzymes. Caveolin-1 physically interacted with HO-1, as shown by coimmunoprecipitation studies. HO activity dramatically increased in cells expressing caveolin-1 antisense transcripts, suggesting a negative regulatory role for caveolin-1. Conversely, caveolin-1 expression attenuated LPS-inducible HO activity. Since their initial characterization in 1969, HO enzymes have been described as endoplasmic reticulum-associated proteins. We demonstrate for the first time the localization of heme degradation enzymes to plasma membrane caveolae, and present novel evidence that caveolin-1 interacts with and modulates HO activity.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Caveolae / enzymology*
  • Caveolae / metabolism
  • Caveolin 1
  • Caveolins / deficiency
  • Caveolins / physiology*
  • Cell Compartmentation
  • Cell Hypoxia
  • Cell Membrane / enzymology
  • Cells, Cultured / enzymology
  • Endoplasmic Reticulum / enzymology
  • Endothelial Cells / enzymology*
  • Endothelial Cells / ultrastructure
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / enzymology*
  • Heme Oxygenase (Decyclizing) / antagonists & inhibitors
  • Heme Oxygenase (Decyclizing) / genetics
  • Heme Oxygenase (Decyclizing) / metabolism*
  • Heme Oxygenase-1
  • Hemin / pharmacology
  • Hepatocytes / enzymology
  • Humans
  • Lipopolysaccharides / pharmacology
  • Membrane Proteins
  • Mice
  • NIH 3T3 Cells / enzymology
  • Nitric Oxide Synthase / metabolism
  • Nitric Oxide Synthase Type II
  • Nitric Oxide Synthase Type III
  • Oligodeoxyribonucleotides, Antisense / pharmacology
  • Oxidoreductases Acting on CH-CH Group Donors / metabolism
  • Protein Interaction Mapping
  • Pulmonary Artery
  • Rats
  • Recombinant Fusion Proteins / metabolism
  • Transfection


  • CAV1 protein, human
  • Cav1 protein, mouse
  • Cav1 protein, rat
  • Caveolin 1
  • Caveolins
  • Lipopolysaccharides
  • Membrane Proteins
  • Oligodeoxyribonucleotides, Antisense
  • Recombinant Fusion Proteins
  • Hemin
  • NOS3 protein, human
  • Nitric Oxide Synthase
  • Nitric Oxide Synthase Type II
  • Nitric Oxide Synthase Type III
  • Nos3 protein, mouse
  • Nos3 protein, rat
  • HMOX1 protein, human
  • Heme Oxygenase (Decyclizing)
  • Heme Oxygenase-1
  • Hmox1 protein, mouse
  • Oxidoreductases Acting on CH-CH Group Donors
  • biliverdin reductase