Affiliations: Malaghan Institute of Medical Research, Wellington,
New Zealand | Department of Radiation Therapy, Wellington School of
Medicine and Health Sciences, University of Otago, Wellington, New
Zealand | Department of Biochemistry, University of Bologna,
Bologna, Italy
Note: [] Address for correspondence: Dr. Michael Berridge, Malaghan
Institute of Medical Research, PO Box 7060, Wellington, New Zealand. Tel.: +64
4 4996914; Fax: +64 4 4996915; E-mail: mberridge@malaghan.org.nz
Abstract: Plasma membrane electron transport (tPMET) pathways have been
identified in all living cells, and a wide variety of tools have been used to
study these processes. In our laboratory we have used the cell-impermeable
tetrazolium dye WST-1, together with the mitochondrial gene
knockout ρ^0) cell model, to investigate one of these
pathways. We have shown that growth of HL60ρ^0 cells is
dependent on oxygen, and that these cells consume oxygen at the cell surface.
Similarities in inhibition profiles between non-mitochondrial oxygen
consumption and WST-1 reduction suggest that both systems share a common tPMET
pathway. In support of this, oxygen was shown to compete with the intermediate
electron acceptor that mediates WST-1 reduction, for reducing electrons. The
observation that tPMET activity is higher in ρ^0 cells
compared to their mitochondrially-competent counterparts was shown to be the
result of competition between the mitochondrial and plasma membrane electron
transport systems for intracellular reducing equivalents. Elevated rates of dye
reduction appear to be mediated through increased expression of the key
components of tPMET, which include the cell surface NADH oxidase, CNOX. These
findings have played a critical role in shaping our current understanding of
the mechanisms of this particular pathway of tPMET.
