Susceptibility to apoptosis in insulin-like growth factor-I receptor-deficient brown adipocytes

Angela M. Valverde, Cecilia Mur, Michael Brownlee, Manuel Benito

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

Fetal brown adipocytes are insulin-like growth factor-I (IGF-I) target cells. To assess the importance of the IGF-I receptor (IGF-IR) in brown adipocytes during fetal life, we have generated immortalized brown adipocyte cell lines from the IGF-IR-/- mice. Using this experimental model, we demonstrate that the lack of IGF-IR in fetal brown adipocytes increased the susceptibility to apoptosis induced by serum withdrawal. Culture of cells in the absence of serum and growth factors produced rapid DNA fragmentation (4 h) in IGF-IR-/- brown adipocytes, compared with the wild type (16 h). Consequently, cell viability was decreased more rapidly in fetal brown adipocytes in the absence of IGF-IR. Furthermore, caspase-3 activity was induced much earlier in cells lacking IGF-IR. At the molecular level, IGF-IR deficiency in fetal brown adipocytes altered the balance of the expression of several proapoptotic (Bcl-xS and Bim) and antiapoptotic (Bcl-2 and Bcl-x L) members of the Bcl-2 family. This imbalance was irreversible even though in IGF-IR-reconstituted cells. Likewise, cytosolic cytochrome c levels increased rapidly in IGF-IR-deficient cells compared with the wild type. A rapid entry of Foxo1 into the nucleus accompanied by a rapid exit from the cytosol and an earlier activation of caspase-8 were observed in brown adipocytes lacking IGF-IR upon serum deprivation. Activation of caspase-8 was inhibited by 50% in both cell types by neutralizing anti-Fas-ligand antibody. Adenoviral infection of wild-type brown adipocytes with constitutively active Foxol (ADA) increased the expression of antiapoptotic genes, decreased Bcl-xL and induced caspase-8 and -3 activities, with the final outcome of DNA fragmentation. Up-regulation of uncoupling protein-1 (UCP-1) expression in IGF-IR-deficient cells by transduction with PGC-1α or UCP-1 ameliorated caspase-3 activation, thereby retarding apoptosis. Finally, insulin treatment prevented apoptosis in both cell types. However, the survival effect of insulin on IGF-IR-/- brown adipocytes was elicited even in the absence of phosphatidylinositol 3-kinase/Akt signaling. Thus, our results demonstrate for the first time the unique role of IGF-IR in maintaining the balance of death and survival in fetal brown adipocytes.

Original languageEnglish (US)
Pages (from-to)5101-5117
Number of pages17
JournalMolecular Biology of the Cell
Volume15
Issue number11
DOIs
StatePublished - Nov 2004

Fingerprint

Brown Adipocytes
IGF Type 1 Receptor
Apoptosis
Caspase 8
Caspase 3
DNA Fragmentation
Serum
Phosphatidylinositol 3-Kinase
Insulin
Fas Ligand Protein
Cytochromes c
Insulin-Like Growth Factor I
Cytosol

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cell Biology

Cite this

Susceptibility to apoptosis in insulin-like growth factor-I receptor-deficient brown adipocytes. / Valverde, Angela M.; Mur, Cecilia; Brownlee, Michael; Benito, Manuel.

In: Molecular Biology of the Cell, Vol. 15, No. 11, 11.2004, p. 5101-5117.

Research output: Contribution to journalArticle

Valverde, Angela M. ; Mur, Cecilia ; Brownlee, Michael ; Benito, Manuel. / Susceptibility to apoptosis in insulin-like growth factor-I receptor-deficient brown adipocytes. In: Molecular Biology of the Cell. 2004 ; Vol. 15, No. 11. pp. 5101-5117.
@article{ec7dbe2d10b14f0cb6318c6710504dff,
title = "Susceptibility to apoptosis in insulin-like growth factor-I receptor-deficient brown adipocytes",
abstract = "Fetal brown adipocytes are insulin-like growth factor-I (IGF-I) target cells. To assess the importance of the IGF-I receptor (IGF-IR) in brown adipocytes during fetal life, we have generated immortalized brown adipocyte cell lines from the IGF-IR-/- mice. Using this experimental model, we demonstrate that the lack of IGF-IR in fetal brown adipocytes increased the susceptibility to apoptosis induced by serum withdrawal. Culture of cells in the absence of serum and growth factors produced rapid DNA fragmentation (4 h) in IGF-IR-/- brown adipocytes, compared with the wild type (16 h). Consequently, cell viability was decreased more rapidly in fetal brown adipocytes in the absence of IGF-IR. Furthermore, caspase-3 activity was induced much earlier in cells lacking IGF-IR. At the molecular level, IGF-IR deficiency in fetal brown adipocytes altered the balance of the expression of several proapoptotic (Bcl-xS and Bim) and antiapoptotic (Bcl-2 and Bcl-x L) members of the Bcl-2 family. This imbalance was irreversible even though in IGF-IR-reconstituted cells. Likewise, cytosolic cytochrome c levels increased rapidly in IGF-IR-deficient cells compared with the wild type. A rapid entry of Foxo1 into the nucleus accompanied by a rapid exit from the cytosol and an earlier activation of caspase-8 were observed in brown adipocytes lacking IGF-IR upon serum deprivation. Activation of caspase-8 was inhibited by 50{\%} in both cell types by neutralizing anti-Fas-ligand antibody. Adenoviral infection of wild-type brown adipocytes with constitutively active Foxol (ADA) increased the expression of antiapoptotic genes, decreased Bcl-xL and induced caspase-8 and -3 activities, with the final outcome of DNA fragmentation. Up-regulation of uncoupling protein-1 (UCP-1) expression in IGF-IR-deficient cells by transduction with PGC-1α or UCP-1 ameliorated caspase-3 activation, thereby retarding apoptosis. Finally, insulin treatment prevented apoptosis in both cell types. However, the survival effect of insulin on IGF-IR-/- brown adipocytes was elicited even in the absence of phosphatidylinositol 3-kinase/Akt signaling. Thus, our results demonstrate for the first time the unique role of IGF-IR in maintaining the balance of death and survival in fetal brown adipocytes.",
author = "Valverde, {Angela M.} and Cecilia Mur and Michael Brownlee and Manuel Benito",
year = "2004",
month = "11",
doi = "10.1091/mbc.E03-11-0853",
language = "English (US)",
volume = "15",
pages = "5101--5117",
journal = "Molecular Biology of the Cell",
issn = "1059-1524",
publisher = "American Society for Cell Biology",
number = "11",

}

TY - JOUR

T1 - Susceptibility to apoptosis in insulin-like growth factor-I receptor-deficient brown adipocytes

AU - Valverde, Angela M.

AU - Mur, Cecilia

AU - Brownlee, Michael

AU - Benito, Manuel

PY - 2004/11

Y1 - 2004/11

N2 - Fetal brown adipocytes are insulin-like growth factor-I (IGF-I) target cells. To assess the importance of the IGF-I receptor (IGF-IR) in brown adipocytes during fetal life, we have generated immortalized brown adipocyte cell lines from the IGF-IR-/- mice. Using this experimental model, we demonstrate that the lack of IGF-IR in fetal brown adipocytes increased the susceptibility to apoptosis induced by serum withdrawal. Culture of cells in the absence of serum and growth factors produced rapid DNA fragmentation (4 h) in IGF-IR-/- brown adipocytes, compared with the wild type (16 h). Consequently, cell viability was decreased more rapidly in fetal brown adipocytes in the absence of IGF-IR. Furthermore, caspase-3 activity was induced much earlier in cells lacking IGF-IR. At the molecular level, IGF-IR deficiency in fetal brown adipocytes altered the balance of the expression of several proapoptotic (Bcl-xS and Bim) and antiapoptotic (Bcl-2 and Bcl-x L) members of the Bcl-2 family. This imbalance was irreversible even though in IGF-IR-reconstituted cells. Likewise, cytosolic cytochrome c levels increased rapidly in IGF-IR-deficient cells compared with the wild type. A rapid entry of Foxo1 into the nucleus accompanied by a rapid exit from the cytosol and an earlier activation of caspase-8 were observed in brown adipocytes lacking IGF-IR upon serum deprivation. Activation of caspase-8 was inhibited by 50% in both cell types by neutralizing anti-Fas-ligand antibody. Adenoviral infection of wild-type brown adipocytes with constitutively active Foxol (ADA) increased the expression of antiapoptotic genes, decreased Bcl-xL and induced caspase-8 and -3 activities, with the final outcome of DNA fragmentation. Up-regulation of uncoupling protein-1 (UCP-1) expression in IGF-IR-deficient cells by transduction with PGC-1α or UCP-1 ameliorated caspase-3 activation, thereby retarding apoptosis. Finally, insulin treatment prevented apoptosis in both cell types. However, the survival effect of insulin on IGF-IR-/- brown adipocytes was elicited even in the absence of phosphatidylinositol 3-kinase/Akt signaling. Thus, our results demonstrate for the first time the unique role of IGF-IR in maintaining the balance of death and survival in fetal brown adipocytes.

AB - Fetal brown adipocytes are insulin-like growth factor-I (IGF-I) target cells. To assess the importance of the IGF-I receptor (IGF-IR) in brown adipocytes during fetal life, we have generated immortalized brown adipocyte cell lines from the IGF-IR-/- mice. Using this experimental model, we demonstrate that the lack of IGF-IR in fetal brown adipocytes increased the susceptibility to apoptosis induced by serum withdrawal. Culture of cells in the absence of serum and growth factors produced rapid DNA fragmentation (4 h) in IGF-IR-/- brown adipocytes, compared with the wild type (16 h). Consequently, cell viability was decreased more rapidly in fetal brown adipocytes in the absence of IGF-IR. Furthermore, caspase-3 activity was induced much earlier in cells lacking IGF-IR. At the molecular level, IGF-IR deficiency in fetal brown adipocytes altered the balance of the expression of several proapoptotic (Bcl-xS and Bim) and antiapoptotic (Bcl-2 and Bcl-x L) members of the Bcl-2 family. This imbalance was irreversible even though in IGF-IR-reconstituted cells. Likewise, cytosolic cytochrome c levels increased rapidly in IGF-IR-deficient cells compared with the wild type. A rapid entry of Foxo1 into the nucleus accompanied by a rapid exit from the cytosol and an earlier activation of caspase-8 were observed in brown adipocytes lacking IGF-IR upon serum deprivation. Activation of caspase-8 was inhibited by 50% in both cell types by neutralizing anti-Fas-ligand antibody. Adenoviral infection of wild-type brown adipocytes with constitutively active Foxol (ADA) increased the expression of antiapoptotic genes, decreased Bcl-xL and induced caspase-8 and -3 activities, with the final outcome of DNA fragmentation. Up-regulation of uncoupling protein-1 (UCP-1) expression in IGF-IR-deficient cells by transduction with PGC-1α or UCP-1 ameliorated caspase-3 activation, thereby retarding apoptosis. Finally, insulin treatment prevented apoptosis in both cell types. However, the survival effect of insulin on IGF-IR-/- brown adipocytes was elicited even in the absence of phosphatidylinositol 3-kinase/Akt signaling. Thus, our results demonstrate for the first time the unique role of IGF-IR in maintaining the balance of death and survival in fetal brown adipocytes.

UR - http://www.scopus.com/inward/record.url?scp=6344269066&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=6344269066&partnerID=8YFLogxK

U2 - 10.1091/mbc.E03-11-0853

DO - 10.1091/mbc.E03-11-0853

M3 - Article

C2 - 15356271

AN - SCOPUS:6344269066

VL - 15

SP - 5101

EP - 5117

JO - Molecular Biology of the Cell

JF - Molecular Biology of the Cell

SN - 1059-1524

IS - 11

ER -