Treatment with panobinostat induces glucose-regulated protein 78 acetylation and endoplasmic reticulum stress in breast cancer cells.
Increased levels of misfolded polypeptides in the endoplasmic reticulum (ER) triggers the dissociation of glucose-regulated protein 78 (GRP78) from the three transmembrane ER-stress mediators, i.e., protein kinase RNA-like ER kinase (PERK), activating transcription factor-6 (ATF6), and inositol-requiring enzyme 1alpha, which results in the adaptive unfolded protein response (UPR). In the present studies, we determined that histone deacetylase-6 (HDAC6) binds and deacetylates GRP78. Following treatment with the pan-histone deacetylase inhibitor panobinostat (Novartis Pharmaceuticals), or knockdown of HDAC6 by short hairpin RNA, GRP78 is acetylated in 11 lysine residues, which dissociates GRP78 from PERK. This is associated with the activation of a lethal UPR in human breast cancer cells. Coimmunoprecipitation studies showed that binding of HDAC6 to GRP78 requires the second catalytic and COOH-terminal BUZ domains of HDAC6. Treatment with panobinostat increased the levels of phosphorylated-eukaryotic translation initiation factor (p-eIF2alpha), ATF4, and CAAT/enhancer binding protein homologous protein (CHOP). Panobinostat treatment also increased the proapoptotic BIK, BIM, BAX, and BAK levels, as well as increased the activity of caspase-7. Knockdown of GRP78 sensitized MCF-7 cells to bortezomib and panobinostat-induced UPR and cell death. These findings indicate that enforced acetylation and decreased binding of GRP78 to PERK is mechanistically linked to panobinostat-induced UPR and cell death of breast cancer cells. Mol Cancer Ther; 9(4); 942-52. (c)2010 AACR.
Rao
Rekha
R
MCG Cancer Center, Medical College of Georgia, 1120 15th Street, CN-2133, Augusta, GA 30912, USA.
Nalluri
Srilatha
S
Kolhe
Ravindra
R
Yang
Yonghua
Y
Fiskus
Warren
W
Chen
Jianguang
J
Ha
Kyungsoo
K
Buckley
Kathleen M
KM
Balusu
Ramesh
R
Coothankandaswamy
Veena
V
Joshi
Atul
A
Atadja
Peter
P
Bhalla
Kapil N
KN
D000107:Acetylation / Q000187:drug effects; D000595:Amino Acid Sequence; D001943:Breast Neoplasms / Q000473:pathology*; D020134:Catalytic Domain; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D004354:Drug Screening Assays, Antitumor; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000473:pathology*; D000091342:Endoplasmic Reticulum Chaperone BiP; D005260:Female; D055785:Gene Knockdown Techniques; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D000073864:Histone Deacetylase 6; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology*; D007211:Indoles; D008954:Models, Biological; D008969:Molecular Sequence Data; D000077767:Panobinostat; D011485:Protein Binding / Q000187:drug effects; D013312:Stress, Physiological / Q000187:drug effects*; D056811:Unfolded Protein Response / Q000187:drug effects; D019892:eIF-2 Kinase / Q000378:metabolism
D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D000073864:Histone Deacetylase 6; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases; D006877:Hydroxamic Acids; D007211:Indoles; D000077767:Panobinostat; D019892:eIF-2 Kinase; C000717247:HSPA5 protein, human; C433811:HDAC6 protein, human