title: The docking protein HEF1 is an apoptotic mediator at focal adhesion sites.
abstract: HEF1 (human enhancer of filamentation 1) is a member of a docking protein family that includes p130(Cas) and Efs. Through assembly of multiple protein interactions at focal adhesion sites, these proteins activate signaling cascades in response to integrin receptor binding of the extracellular matrix. The HEF1 protein is cell cycle regulated, with full-length forms cleaved in mitosis at a caspase consensus site to generate an amino-terminal 55-kDa form that localizes to the mitotic spindle. The identification of a caspase cleavage site in HEF1 led us to investigate whether HEF1 belongs to a select group of caspase substrates cleaved in apoptosis to promote the morphological changes characteristic of programmed cell death. Significantly, inducing expression of HEF1 in MCF-7 or HeLa cells causes extensive apoptosis, as assessed by multiple criteria. Endogenous HEF1 is cleaved into 65- and 55-kDa fragments and a newly detected 28-kDa form in response to the induction of apoptosis, paralleling cleavage of poly(ADP-ribose) polymerase and focal adhesion kinase (FAK); the death-promoting activity of over-expressed HEF1 is associated with production of the 28-kDa form. While the generation of the cleaved HEF1 forms is caspase dependent, the accumulation of HEF1 forms is further regulated by the proteasome, as the proteasome inhibitors N-acetyl-L-leucinyl-L-leucinyl-L-norleucinyl and lactacystin enhance their stability. Finally, the induction of HEF1 expression also increases Jun N-terminal protein kinase (JNK) activation, and activated JNK colocalizes with HEF1, implicating this pathway in HEF1 action. Based on these results, we propose that dysregulation of HEF1 and its family members along with FAK may signal the destruction of focal adhesion sites and regulate the onset of apoptosis.
authors.affiliation: Division of Basic Science, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
authors.forename: S F
authors.initials: SF
authors.lastname: Law
authors.forename: G M
authors.initials: GM
authors.lastname: O'Neill
authors.forename: S J
authors.initials: SJ
authors.lastname: Fashena
authors.forename: M B
authors.initials: MB
authors.lastname: Einarson
authors.forename: E A
authors.initials: EA
authors.lastname: Golemis
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053148:Caspase 3; D053179:Caspase 7; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000502:physiology; D050719:Crk-Associated Substrate Protein; D003546:Cysteine Endopeptidases / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006367:HeLa Cells; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D007976:Leupeptins / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008938:Mitosis; D009097:Multienzyme Complexes / Q000378:metabolism; D009154:Mutation; D009842:Oligopeptides / Q000494:pharmacology; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D020033:Protein Isoforms / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins; D050717:Retinoblastoma-Like Protein p130; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C493841:BCAR1 protein, human; D061945:Caspase Inhibitors; D050719:Crk-Associated Substrate Protein; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D009097:Multienzyme Complexes; C099942:NEDD9 protein, human; D009842:Oligopeptides; D010446:Peptide Fragments; D010750:Phosphoproteins; D020033:Protein Isoforms; D011506:Proteins; D050717:Retinoblastoma-Like Protein p130; D014409:Tumor Necrosis Factor-alpha; C110772:benzoylcarbonyl-aspartyl-glutamyl-valyl-aspartyl-fluoromethyl ketone; C063261:acetylleucyl-leucyl-norleucinal; C067713:lactacystin; D011065:Poly(ADP-ribose) Polymerases; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; C505520:CASP7 protein, human; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D000111:Acetylcysteine