title: Hsp70B' regulation and function.
abstract: Heat shock protein (Hsp) 70B' is a human Hsp70 chaperone that is strictly inducible, having little or no basal expression levels in most cells. Using siRNAs to knockdown Hsp70B' and Hsp72 in HT-29, SW-480, and CRL-1807 human colon cell lines, we have found that the two are regulated coordinately in response to stress. We also have found that proteasome inhibition is a potent activator of hsp70B'. Flow cytometry was used to assay hsp70B' promoter activity in HT-29eGFP cells in this study. Knockdown of both Hsp70B' and Hsp72 sensitized cells to heat stress and increasing concentrations of proteasome inhibitor. These data support the conclusion that Hsp72 is the primary Hsp70 family responder to increasing levels of proteotoxic stress, and Hsp70B' is a secondary responder. Interestingly ZnSO4 induces Hsp70B' and not Hsp72 in CRL-1807 cells, suggesting a stressor-specific primary role for Hsp70B'. Both Hsp70B' and Hsp72 are important for maintaining viability under conditions that increase the accumulation of damaged proteins in HT-29 cells. These findings are likely to be important in pathological conditions in which Hsp70B' contributes to cell survival.
authors.affiliation: Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269-3125, USA. emily.noonan@gmail.com
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Noonan
authors.forename: Robert F
authors.initials: RF
authors.lastname: Place
authors.forename: Charles
authors.initials: C
authors.lastname: Giardina
authors.forename: Lawrence E
authors.initials: LE
authors.lastname: Hightower
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D005434:Flow Cytometry; D049452:Green Fluorescent Proteins / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D050884:HSP72 Heat-Shock Proteins / Q000378:metabolism; D019073:HT29 Cells; D018869:Heat-Shock Response / Q000187:drug effects; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D061988:Proteasome Inhibitors; D034741:RNA, Small Interfering / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D018840:HSP70 Heat-Shock Proteins; D050884:HSP72 Heat-Shock Proteins; C491129:HSPA7 protein, human; D007976:Leupeptins; D061988:Proteasome Inhibitors; D034741:RNA, Small Interfering; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde