RATIONALE: Alternative splicing provides a versatile mechanism by which cells generate proteins with different or even antagonistic properties. Previously, we established hypoxia-inducible death factor Bnip3 as a critical component of the intrinsic death pathway. OBJECTIVE: To investigate alternative splicing of Bnip3 pre-mRNA in postnatal ventricular myocytes during hypoxia. METHODS AND RESULTS: We identify a novel previously unrecognized spliced variant of Bnip3 (Bnip3Δex3) generated by alternative splicing of exon3 exclusively in cardiac myocytes subjected to hypoxia. Sequencing of Bnip3Δex3 revealed a frame shift mutation that terminated transcription up-stream of exon5 and exon6 ablating translation of the BH3-like domain and critical carboxyl-terminal transmembrane domain crucial for mitochondrial localization and cell death. Notably, although the 26-kDa Bnip3 protein (Bnip3FL) encoded by full-length mRNA was localized to mitochondria and provoked cell death, the 8.2-kDa Bnip3Δex3 protein encoded by the truncated spliced mRNA was defective for mitochondrial targeting but interacted with Bnip3FL resulting in less association of Bnip3FL with mitochondria and diminished apoptotic and necrotic cell death. Forced expression of Bnip3FL in cardiac myocytes or Bnip3(-/-) mouse embryonic fibroblasts triggered widespread cell death that was inhibited by coexpression of Bnip3Δex3. Conversely, RNA interference targeted against sequences encompassing the unique exon2-exon4 junction of the Bnip3Δex3 sensitized cardiac myocytes to mitochondrial perturbations and cell death induced by Bnip3FL. CONCLUSIONS: Given the otherwise lethal consequences of deregulated Bnip3FL expression in postmitotic cells, our findings reveal a novel intrinsic defense mechanism that opposes the mitochondrial defects and cell death of ventricular myocytes that is obligatorily linked and mutually dependent on alternative splicing of Bnip3FL during hypoxia or ischemic stress.
RATIONALE: Alternative splicing provides a versatile mechanism by which cells generate proteins with different or even antagonistic properties. Previously, we established hypoxia-inducible death factor Bnip3 as a critical component of the intrinsic death pathway. OBJECTIVE: To investigate alternative splicing of Bnip3 pre-mRNA in postnatal ventricular myocytes during hypoxia. METHODS AND RESULTS: We identify a novel previously unrecognized spliced variant of Bnip3 (Bnip3Δex3) generated by alternative splicing of exon3 exclusively in cardiac myocytes subjected to hypoxia. Sequencing of Bnip3Δex3 revealed a frame shift mutation that terminated transcription up-stream of exon5 and exon6 ablating translation of the BH3-like domain and critical carboxyl-terminal transmembrane domain crucial for mitochondrial localization and cell death. Notably, although the 26-kDa Bnip3 protein (Bnip3FL) encoded by full-length mRNA was localized to mitochondria and provoked cell death, the 8.2-kDa Bnip3Δex3 protein encoded by the truncated spliced mRNA was defective for mitochondrial targeting but interacted with Bnip3FL resulting in less association of Bnip3FL with mitochondria and diminished apoptotic and necrotic cell death. Forced expression of Bnip3FL in cardiac myocytes or Bnip3(-/-) mouse embryonic fibroblasts triggered widespread cell death that was inhibited by coexpression of Bnip3Δex3. Conversely, RNA interference targeted against sequences encompassing the unique exon2-exon4 junction of the Bnip3Δex3 sensitized cardiac myocytes to mitochondrial perturbations and cell death induced by Bnip3FL. CONCLUSIONS: Given the otherwise lethal consequences of deregulated Bnip3FL expression in postmitotic cells, our findings reveal a novel intrinsic defense mechanism that opposes the mitochondrial defects and cell death of ventricular myocytes that is obligatorily linked and mutually dependent on alternative splicing of Bnip3FL during hypoxia or ischemic stress.
Authors: Calvin Yeang; Devin Hasanally; Xuchu Que; Ming-Yow Hung; Aleksandra Stamenkovic; David Chan; Rakesh Chaudhary; Victoria Margulets; Andrea L Edel; Masahiko Hoshijima; Yusu Gu; William Bradford; Nancy Dalton; Phuong Miu; David Yc Cheung; Davinder S Jassal; Grant N Pierce; Kirk L Peterson; Lorrie A Kirshenbaum; Joseph L Witztum; Sotirios Tsimikas; Amir Ravandi Journal: Cardiovasc Res Date: 2019-01-01 Impact factor: 10.787
Authors: Akram Alyass; Peter Almgren; Mikael Akerlund; Jonathan Dushoff; Bo Isomaa; Peter Nilsson; Tiinamaija Tuomi; Valeriya Lyssenko; Leif Groop; David Meyre Journal: Diabetologia Date: 2014-10-08 Impact factor: 10.122
Authors: Rimpy Dhingra; Matthew Guberman; Inna Rabinovich-Nikitin; Jonathon Gerstein; Victoria Margulets; Hongying Gang; Nicholas Madden; James Thliveris; Lorrie A Kirshenbaum Journal: Cardiovasc Res Date: 2020-05-01 Impact factor: 10.787
Authors: Rimpy Dhingra; Victoria Margulets; Subir Roy Chowdhury; James Thliveris; Davinder Jassal; Paul Fernyhough; Gerald W Dorn; Lorrie A Kirshenbaum Journal: Proc Natl Acad Sci U S A Date: 2014-12-08 Impact factor: 11.205