Novel function of PERK as a mediator of force-induced apoptosis.
Induction of apoptosis by tensile forces is an important determinant of connective tissue destruction in osteoarthritis and periodontal diseases. We examined the role of molecular components of the unfolded protein response in force-induced apoptosis. Magnetic fields were used to apply tensile force through integrins to cultured fibroblasts bound with collagen-coated magnetite beads. Tensile force induced caspase 3 cleavage, DNA fragmentation, depolarization of mitochondria, and induction of CHOP10, all indicative of activation of apoptosis. Immunoblotting, immunocytochemistry, and release of Ca(2+) from the endoplasmic reticulum showed evidence for both physical and functional associations between bound beads and the endoplasmic reticulum. Force-induced apoptosis was not detected in PERK null cells, but reconstitution of wild-type PERK in PERK null cells restored the apoptotic response. Force-induced apoptosis did not require PKR, GCN2, eIF2alpha, or CHOP10. Furthermore, force more than 24 h did not activate other initiators of the unfolded protein response including IRE-1 and ATF6. However, force-induced activation of caspase 3 was dependent on caspase 9 but was independent of mitochondria. We conclude that force-induced apoptosis depends on a novel function of PERK that occurs in addition to its canonical role in the unfolded protein response.
Canadian Institutes of Health Research Group in Matrix Dynamics, University of Toronto, Toronto, Ontario M5S 3E2, Canada.
Baldwin C
BC
Mak
Qin
Q
Wang
Carol
C
Laschinger
Wilson
W
Lee
David
D
Ron
Heather P
HP
Harding
Randal J
RJ
Kaufman
Donalyn
D
Scheuner
Richard C
RC
Austin
Christopher A
CA
McCulloch
D051702:Activating Transcription Factor 6; D000818:Animals; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013314:Stress, Mechanical; D013718:Tensile Strength; D051742:Transcription Factor CHOP / Q000378:metabolism; D019892:eIF-2 Kinase / Q000737:chemistry / Q000502:physiology*
D051702:Activating Transcription Factor 6; D053148:Caspase 3; D053453:Caspase 9; D008565:Membrane Proteins; D017346:Protein Serine-Threonine Kinases; D051742:Transcription Factor CHOP; D019892:eIF-2 Kinase; C497112:Atf6 protein, mouse; C497250:Ddit3 protein, mouse; C486556:Ern2 protein, mouse