Hispolon promotes MDM2 downregulation through chaperone-mediated autophagy

Te Ling Lu, Guan Jhong Huang, Huang Joe Wang, Jian Lian Chen, Hui-Ping Hsu, Te Jung Lu

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Amplification and overexpression of murine double minute (MDM2) has been observed in several human cancers. Some chemotherapeutic agents cause MDM2 ubiquitination and degradation in a proteasome-dependent system. In addition to the proteasome system, chaperone-mediated autophagy (CMA) is a lysosomal pathway for selective misfolded protein degradation. Molecular chaperone heat shock cognate 70 protein (Hsc70) recognizes the misfolded proteins, which are then delivered to lysosome-associated membrane protein type 2A (LAMP2A) for lysosomal degradation. Our previous study reported that hispolon was able to induce cell apoptosis and downregulate MDM2 expression. In this study, our results showed that the proteasome inhibitor, MG132, could not inhibit hispolon-induced MDM2 downregulation. In contrast, both inhibition of lysosomes with NH4Cl and inhibition of LAMP2A using siRNA partially attenuated hispolon-induced MDM2 downregulation. To determine whether Hsc70 recognizes MDM2 on amino acids 135-141, SMP14 antibody was used to compete with Hsc70 for interaction with MDM2. After Hsc70 knockdown, SMP14 antibody immunoprecipitated increased MDM2. We also found that hispolon induced increased association of Hsp70, Hsc70, Hsp90 and LAMP2A with MDM2. This association was inhibited in cells pretreated with geldanamycin (GA), an Hsp90 inhibitor. GA also attenuated hispolon-induced MDM2 downregulation. Meanwhile, inhibition of Hsc70 using siRNA attenuated hispolon-induced MDM2 downregulation. Our study provides the first example of the ability of hispolon to mediate MDM2 downregulation in lysosomes through the CMA pathway.

Original languageEnglish
Pages (from-to)26-31
Number of pages6
JournalBiochemical and Biophysical Research Communications
Volume398
Issue number1
DOIs
Publication statusPublished - 2010 Jul 1

Fingerprint

HSC70 Heat-Shock Proteins
Autophagy
Down-Regulation
Lysosome-Associated Membrane Glycoproteins
Proteasome Endopeptidase Complex
Lysosomes
Degradation
Small Interfering RNA
Association reactions
Proteasome Inhibitors
Molecular Chaperones
Antibodies
Ubiquitination
hispolon
Proteolysis
Amplification
Proteins
Apoptosis
Amino Acids

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Lu, Te Ling ; Huang, Guan Jhong ; Wang, Huang Joe ; Chen, Jian Lian ; Hsu, Hui-Ping ; Lu, Te Jung. / Hispolon promotes MDM2 downregulation through chaperone-mediated autophagy. In: Biochemical and Biophysical Research Communications. 2010 ; Vol. 398, No. 1. pp. 26-31.
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abstract = "Amplification and overexpression of murine double minute (MDM2) has been observed in several human cancers. Some chemotherapeutic agents cause MDM2 ubiquitination and degradation in a proteasome-dependent system. In addition to the proteasome system, chaperone-mediated autophagy (CMA) is a lysosomal pathway for selective misfolded protein degradation. Molecular chaperone heat shock cognate 70 protein (Hsc70) recognizes the misfolded proteins, which are then delivered to lysosome-associated membrane protein type 2A (LAMP2A) for lysosomal degradation. Our previous study reported that hispolon was able to induce cell apoptosis and downregulate MDM2 expression. In this study, our results showed that the proteasome inhibitor, MG132, could not inhibit hispolon-induced MDM2 downregulation. In contrast, both inhibition of lysosomes with NH4Cl and inhibition of LAMP2A using siRNA partially attenuated hispolon-induced MDM2 downregulation. To determine whether Hsc70 recognizes MDM2 on amino acids 135-141, SMP14 antibody was used to compete with Hsc70 for interaction with MDM2. After Hsc70 knockdown, SMP14 antibody immunoprecipitated increased MDM2. We also found that hispolon induced increased association of Hsp70, Hsc70, Hsp90 and LAMP2A with MDM2. This association was inhibited in cells pretreated with geldanamycin (GA), an Hsp90 inhibitor. GA also attenuated hispolon-induced MDM2 downregulation. Meanwhile, inhibition of Hsc70 using siRNA attenuated hispolon-induced MDM2 downregulation. Our study provides the first example of the ability of hispolon to mediate MDM2 downregulation in lysosomes through the CMA pathway.",
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Hispolon promotes MDM2 downregulation through chaperone-mediated autophagy. / Lu, Te Ling; Huang, Guan Jhong; Wang, Huang Joe; Chen, Jian Lian; Hsu, Hui-Ping; Lu, Te Jung.

In: Biochemical and Biophysical Research Communications, Vol. 398, No. 1, 01.07.2010, p. 26-31.

Research output: Contribution to journalArticle

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AU - Lu, Te Ling

AU - Huang, Guan Jhong

AU - Wang, Huang Joe

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