Hexokinase-I protection against apoptotic cell death is mediated via interaction with the voltage-dependent anion channel-1: mapping the site of binding.
In brain and tumor cells, the hexokinase isoforms HK-I and HK-II bind to the voltage-dependent anion channel (VDAC) in the outer mitochondrial membrane. We have previously shown that HK-I decreases murine VDAC1 (mVDAC1) channel conductance, inhibits cytochrome c release, and protects against apoptotic cell death. Now, we define mVDAC1 residues, found in two cytoplasmic domains, involved in the interaction with HK-I. Protection against cell death by HK-I, as induced by overexpression of native or mutated mVDAC1, served to identify the mVDAC1 amino acids required for interaction with HK-I. HK-I binding to mVDAC1 either in isolated mitochondria or reconstituted in a bilayer was inhibited upon mutation of specific VDAC1 residues. HK-I anti-apoptotic activity was also diminished upon mutation of these amino acids. HK-I-mediated inhibition of cytochrome c release induced by staurosporine was also diminished in cells expressing VDAC1 mutants. Our results thus offer new insights into the mechanism by which HK-I promotes tumor cell survival via inhibition of cytochrome c release through HK-I binding to VDAC1. These results, moreover, point to VDAC1 as a key player in mitochondrially mediated apoptosis and implicate an HK-I-VDAC1 interaction in the regulation of apoptosis. Finally, these findings suggest that interference with the binding of HK-I to mitochondria by VDAC1-derived peptides may offer a novel strategy by which to potentiate the efficacy of conventional chemotherapeutic agents.
Abu-Hamad
Salah
S
Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.
Zaid
Hilal
H
Israelson
Adrian
A
Nahon
Edna
E
Shoshan-Barmatz
Varda
V
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001665:Binding Sites; D002460:Cell Line; D017124:Conserved Sequence; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D005786:Gene Expression Regulation; D006593:Hexokinase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D016415:Sequence Alignment; D050995:Voltage-Dependent Anion Channel 1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D047428:Protein Kinase Inhibitors; D045304:Cytochromes c; D050995:Voltage-Dependent Anion Channel 1; D006593:Hexokinase