Disruption of cytochrome c heme coordination is responsible for mitochondrial injury during ischemia

Alexander V Birk; Wesley M Chao; Shaoyi Liu; Yi Soong; Hazel H Szeto

doi:10.1016/j.bbabio.2015.06.006

Disruption of cytochrome c heme coordination is responsible for mitochondrial injury during ischemia

Biochim Biophys Acta. 2015 Oct;1847(10):1075-84. doi: 10.1016/j.bbabio.2015.06.006. Epub 2015 Jun 10.

Authors

Alexander V Birk¹, Wesley M Chao¹, Shaoyi Liu¹, Yi Soong¹, Hazel H Szeto²

Affiliations

¹ Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell University, New York, NY 10065, USA; Research Program in Mitochondrial Therapeutics, Joan and Sanford I. Weill Medical College of Cornell University, New York, NY 10065, USA.
² Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell University, New York, NY 10065, USA; Research Program in Mitochondrial Therapeutics, Joan and Sanford I. Weill Medical College of Cornell University, New York, NY 10065, USA. Electronic address: hhszeto@med.cornell.edu.

Abstract

Background: It was recently suggested that electron flow into cyt c, coupled with ROS generation, oxidizes cyt c Met(80) to Met(80) sulfoxide (Met-O) in isolated hearts after ischemia-reperfusion, and converts cyt c to a peroxidase. We hypothesize that ischemia disrupts Met(80)-Fe ligation of cyt c, forming pentacoordinated heme Fe(2+), which inhibits electron transport (ET) and promotes oxygenase activity.

Methods: SS-20 (Phe-D-Arg-Phe-Lys-NH2) was used to demonstrate the role of Met(80)-Fe ligation in ischemia. Mitochondria were isolated from ischemic rat kidneys to determine sites of respiratory inhibition. Mitochondrial cyt c and cyt c Met-O were quantified by western blot, and cristae architecture was examined by electron microscopy.

Results: Biochemical and structural studies showed that SS-20 selectively targets cardiolipin (CL) and protects Met(80)-Fe ligation in cyt c. Ischemic mitochondria showed 17-fold increase in Met-O cyt c, and dramatic cristaeolysis. Loss of cyt c was associated with proteolytic degradation of OPA1. Ischemia significantly inhibited ET initiated by direct reduction of cyt c and coupled respiration. All changes were prevented by SS-20.

Conclusion: Our results show that ischemia disrupts the Met(80)-Fe ligation of cyt c resulting in the formation of a globin-like pentacoordinated heme Fe(2+) that inhibits ET, and converts cyt c into an oxygenase to cause CL peroxidation and proteolytic degradation of OPA1, resulting in cyt c release.

General significance: Cyt c heme structure represents a novel target for minimizing ischemic injury. SS-20, which we show to selectively target CL and protect the Met(80)-Fe ligation, minimizes ischemic injury and promotes ATP recovery.

Keywords: Electron transport; Methionine sulfoxide; Mitochondria cristae; OPA1; SS-20; cyt c oxygenase.

Abstract

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