title: Human and murine granzyme B exhibit divergent substrate preferences.
abstract: The cytotoxic lymphocyte protease granzyme B (GzmB) can promote apoptosis through direct processing and activation of members of the caspase family. GzmB can also cleave the BH3-only protein, BID, to promote caspase-independent mitochondrial permeabilization. Although human and mouse forms of GzmB exhibit extensive homology, these proteases diverge at residues predicted to influence substrate binding. We show that human and mouse GzmB exhibit radical differences in their ability to cleave BID, as well as several other key substrates, such as ICAD and caspase-8. Moreover, pharmacological inhibition of caspases clonogenically rescued human and mouse target cells from apoptosis initiated by mouse GzmB, but failed to do so in response to human GzmB. These data demonstrate that human and murine GzmB are distinct enzymes with different substrate preferences. Our observations also illustrate how subtle differences in enzyme structure can radically affect substrate selection.
authors.affiliation: Molecular Cell Biology Laboratory, Department of Genetics, The Smurfit Institute, Trinity College, Dublin 2, Ireland.
authors.forename: Sean P
authors.initials: SP
authors.lastname: Cullen
authors.forename: Colin
authors.initials: C
authors.lastname: Adrain
authors.forename: Alexander U
authors.initials: AU
authors.lastname: Lüthi
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Duriez
authors.forename: Seamus J
authors.initials: SJ
authors.lastname: Martin
mesh_terms: D000595:Amino Acid Sequence / Q000502:physiology; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism*; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D053804:Granzymes / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D013045:Species Specificity; D013379:Substrate Specificity; D013602:T-Lymphocytes, Cytotoxic / Q000201:enzymology* / Q000276:immunology
chemical_list: D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein; C494815:Bid protein, mouse; D053804:Granzymes; D020169:Caspases