A cardiac myocyte-restricted Lin28/let-7 regulatory axis promotes hypoxia-mediated apoptosis by inducing the AKT signaling suppressor PIK3IP1

Shaurya Joshi, Jianqin Wei, Nanette Bishopric

Research output: Contribution to journalArticle

17 Scopus citations


Rationale: The let-7 family of microRNAs (miRs) regulates critical cell functions, including survival signaling, differentiation, metabolic control and glucose utilization. These functions may be important during myocardial ischemia. MiR-let-7 expression is under tight temporal and spatial control through multiple redundant mechanisms that may be stage-, isoform- and tissue-specific. Objective: To determine the mechanisms and functional consequences of miR-let-7 regulation by hypoxia in the heart. Methods and results: MiR-let-7a, -7c and -7g were downregulated in the adult mouse heart early after coronary occlusion, and in neonatal rat ventricular myocytes subjected to hypoxia. Let-7 repression did not require glucose depletion, and occurred at a post-transcriptional level. Hypoxia also induced the RNA binding protein Lin28, a negative regulator of let-7. Hypoxia ineither induced Lin28 nor repressed miR-let-7 in cardiac fibroblasts. Both changes were abrogated by treatment with the histone deacetylase inhibitor trichostatin A. Restoration of let-7g to hypoxic myocytes and to ischemia-reperfused mouse hearts in vivo via lentiviral transduction potentiated the hypoxia-induced phosphorylation and activation of Akt, and prevented hypoxia-dependent caspase activation and death. Mechanistically, phosphatidyl inositol 3-kinase interacting protein 1 (Pik3ip1), a negative regulator of PI3K, was identified as a novel target of miR-let-7 by a crosslinking technique showing that miR-let-7g specifically targets Pik3ip1 to the cardiac myocyte Argonaute complex RISC. Finally, in non-failing and failing human myocardium, we found specific inverse relationships between Lin28 and miR-let-7g, and between miR-let-7g and PIK3IP1. Conclusion: A conserved hypoxia-responsive Lin28-miR-let-7-Pik3ip1 regulatory axis is specific to cardiac myocytes and promotes apoptosis during myocardial ischemic injury.

Original languageEnglish (US)
Pages (from-to)240-251
Number of pages12
JournalBiochimica et Biophysica Acta - Molecular Basis of Disease
Issue number2
StatePublished - Feb 1 2016



  • AKT
  • Apoptosis
  • Ischemia-reperfusion
  • Let-7
  • Lin28
  • PIK3IP1

ASJC Scopus subject areas

  • Molecular Biology
  • Molecular Medicine

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