Effects of targeted Bcl-2 expression in mitochondria or endoplasmic reticulum on renal tubular cell apoptosis

Kirti Bhatt, Leping Feng, Navjotsingh Pabla, Kebin Liu, Sylvia B Smith, Zheng Dong

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

Bcl-2 family proteins are central regulators of apoptosis. As the prototypic member, Bcl-2 protects various types of cells against apoptotic insults. In mammalian cells, Bcl-2 has a dual subcellular localization, in mitochondria and endoplasmic reticulum (ER). The respective roles played by mitochondrial and ER-localized Bcl-2 in apoptotic inhibition are unclear. Using Bcl-2 constructs for targeted subcellular expression, we have now determined the contributions of mitochondrial and ER-localized Bcl-2 to the antiapoptotic effects of Bcl-2 in renal tubular cells. Wild-type Bcl-2, when expressed in renal proximal tubular cells, showed partial colocalizations with both cytochrome c and disulfide isomerase, indicating dual localizations of Bcl-2 in mitochondria and ER. In contrast, Bcl-2 constructs with mitochondria-targeting or ER-targeting sequences led to relatively restricted Bcl-2 expression in mitochondria and ER, respectively. Expression of wild-type and mitochondrial Bcl-2 showed significant inhibitory effects on tubular cell apoptosis that was induced by cisplatin or ATP depletion; however, ER-Bcl-2 was much less effective. During ATP depletion, cytochrome c was released from mitochondria into the cytosol. This release was suppressed by wild-type and mitochondrial Bcl-2, but not by ER-Bcl-2. Consistently, wild-type and mitochondrial Bcl-2, but not ER-Bcl-2, blocked Bax activation during ATP depletion, a critical event for mitochondrial outer membrane permeabilization and cytochrome c release. In contrast, ER-Bcl-2 protected against apoptosis during tunicamycin-induced ER stress. Collectively, the results suggest that the cytoprotective effects of Bcl-2 in different renal injury models are largely determined by its subcellular localizations.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Renal Physiology
Volume294
Issue number3
DOIs
StatePublished - Mar 1 2008

Fingerprint

Endoplasmic Reticulum
Mitochondria
Apoptosis
Kidney
Cytochromes c
Adenosine Triphosphate
Protein Disulfide-Isomerases
Tunicamycin
Endoplasmic Reticulum Stress
Mitochondrial Membranes
Cytosol
Cisplatin
Wounds and Injuries

Keywords

  • Adenosine 5′-triphosphate depletion
  • Apoptosis
  • Bcl-2
  • Cisplatin
  • Endoplasmic reticulum
  • Mitochondria

ASJC Scopus subject areas

  • Physiology
  • Urology

Cite this

Effects of targeted Bcl-2 expression in mitochondria or endoplasmic reticulum on renal tubular cell apoptosis. / Bhatt, Kirti; Feng, Leping; Pabla, Navjotsingh; Liu, Kebin; Smith, Sylvia B; Dong, Zheng.

In: American Journal of Physiology - Renal Physiology, Vol. 294, No. 3, 01.03.2008.

Research output: Contribution to journalArticle

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AB - Bcl-2 family proteins are central regulators of apoptosis. As the prototypic member, Bcl-2 protects various types of cells against apoptotic insults. In mammalian cells, Bcl-2 has a dual subcellular localization, in mitochondria and endoplasmic reticulum (ER). The respective roles played by mitochondrial and ER-localized Bcl-2 in apoptotic inhibition are unclear. Using Bcl-2 constructs for targeted subcellular expression, we have now determined the contributions of mitochondrial and ER-localized Bcl-2 to the antiapoptotic effects of Bcl-2 in renal tubular cells. Wild-type Bcl-2, when expressed in renal proximal tubular cells, showed partial colocalizations with both cytochrome c and disulfide isomerase, indicating dual localizations of Bcl-2 in mitochondria and ER. In contrast, Bcl-2 constructs with mitochondria-targeting or ER-targeting sequences led to relatively restricted Bcl-2 expression in mitochondria and ER, respectively. Expression of wild-type and mitochondrial Bcl-2 showed significant inhibitory effects on tubular cell apoptosis that was induced by cisplatin or ATP depletion; however, ER-Bcl-2 was much less effective. During ATP depletion, cytochrome c was released from mitochondria into the cytosol. This release was suppressed by wild-type and mitochondrial Bcl-2, but not by ER-Bcl-2. Consistently, wild-type and mitochondrial Bcl-2, but not ER-Bcl-2, blocked Bax activation during ATP depletion, a critical event for mitochondrial outer membrane permeabilization and cytochrome c release. In contrast, ER-Bcl-2 protected against apoptosis during tunicamycin-induced ER stress. Collectively, the results suggest that the cytoprotective effects of Bcl-2 in different renal injury models are largely determined by its subcellular localizations.

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