title: Hsc70 contributes to cancer cell survival by preventing Rab1A degradation under stress conditions.
abstract: Heat shock cognate protein 70 (Hsc70) acts as a molecular chaperone for the maintenance of intracellular proteins, which allows cancer cells to survive under proteotoxic stress. We attempted to use Hsc70 to identify key molecules in cancer cell survival. Here, we performed mass-spectrometry-based proteomics analysis utilizing affinity purification with anti-Hsc70 antibodies; as a result, 83 differentially expressed proteins were identified under stress conditions. This result implies that there was a change in the proteins with which Hsc70 interacted in response to stress. Among the proteins identified under both serum-depleted and 5-fluorouracil-treated conditions, Rab1A was identified as an essential molecule for cancer cell survival. Hsc70 interacted with Rab1A in a chaperone-dependent manner. In addition, Hsc70 knockdown decreased the level of Rab1A and increased the level of its ubiquitination under stress conditions, suggesting that Hsc70 prevented the degradation of Rab1A denatured by stress exposure. We also found that Rab1A knockdown induced cell death by inhibition of autophagosome formation. Rab1A may therefore contribute to overcoming proteotoxic insults, which allows cancer cells to survive under stress conditions. Analysis of Hsc70 interactors provided insight into changes of intracellular status. We expect further study of the Hsc70 interactome to provide a more comprehensive understanding of cancer cell physiology.
authors.affiliation: Department of Pharmacology, Osaka City University Medical School, Osaka, Japan.
authors.forename: Masako
authors.initials: M
authors.lastname: Tanaka
authors.affiliation: Department of Pharmacology, Osaka City University Medical School, Osaka, Japan.
authors.forename: Saya
authors.initials: S
authors.lastname: Mun
authors.affiliation: Department of Advanced Medical Initiatives, Faculty of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Akihito
authors.initials: A
authors.lastname: Harada
authors.affiliation: Department of Advanced Medical Initiatives, Faculty of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Ohkawa
authors.affiliation: Department of Pathology, Osaka City University Medical School, Osaka, Japan.
authors.forename: Azusa
authors.initials: A
authors.lastname: Inagaki
authors.affiliation: Department of Cardiovascular Medicine, Osaka City University Medical School, Osaka, Japan.
authors.forename: Soichi
authors.initials: S
authors.lastname: Sano
authors.affiliation: Department of Pharmacology, Osaka City University Medical School, Osaka, Japan.
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Takahashi
authors.affiliation: Department of Pharmacology, Osaka City University Medical School, Osaka, Japan.
authors.forename: Yasukatsu
authors.initials: Y
authors.lastname: Izumi
authors.affiliation: Department of Pharmacology, Osaka City University Medical School, Osaka, Japan.
authors.forename: Mayuko
authors.initials: M
authors.lastname: Osada-Oka
authors.affiliation: Department of Pathology, Osaka City University Medical School, Osaka, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Wanibuchi
authors.affiliation: Laboratory of Clinical Pharmacology, Faculty of Pharmacy, Osaka Ohtani University, Tondabayashi, Japan.
authors.forename: Masayo
authors.initials: M
authors.lastname: Yamagata
authors.affiliation: Laboratory of Clinical Pharmacology, Faculty of Pharmacy, Osaka Ohtani University, Tondabayashi, Japan.
authors.forename: Tokihito
authors.initials: T
authors.lastname: Yukimura
authors.affiliation: Applied Pharmacology and Therapeutics, Osaka City University Medical School, Osaka, Japan.
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Miura
authors.affiliation: Department of Pharmacology, Osaka City University Medical School, Osaka, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Shiota
authors.affiliation: Department of Pharmacology, Osaka City University Medical School, Osaka, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Iwao
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D005472:Fluorouracil / Q000633:toxicity; D005786:Gene Expression Regulation; D050883:HSC70 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D019073:HT29 Cells; D006801:Humans; D040081:Protein Array Analysis; D011506:Proteins / Q000032:analysis / Q000378:metabolism; D040901:Proteomics; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D020761:rab1 GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D050883:HSC70 Heat-Shock Proteins; D011506:Proteins; D034741:RNA, Small Interfering; D020761:rab1 GTP-Binding Proteins; D005472:Fluorouracil