title: Isoform-selective Genetic Inhibition of Constitutive Cytosolic Hsp70 Activity Promotes Client Tau Degradation Using an Altered Co-chaperone Complement.
abstract: The constitutively expressed heat shock protein 70 kDa (Hsc70) is a major chaperone protein responsible for maintaining proteostasis, yet how its structure translates into functional decisions regarding client fate is still unclear. We previously showed that Hsc70 preserved aberrant Tau, but it remained unknown if selective inhibition of the activity of this Hsp70 isoform could facilitate Tau clearance. Using single point mutations in the nucleotide binding domain, we assessed the effect of several mutations on the functions of human Hsc70. Biochemical characterization revealed that one mutation abolished both Hsc70 ATPase and refolding activities. This variant resembled the ADP-bound conformer at all times yet remained able to interact with cofactors, nucleotides, and substrates appropriately, resembling a dominant negative Hsc70 (DN-Hsc70). We then assessed the effects of this DN-Hsc70 on its client Tau. DN-Hsc70 potently facilitated Tau clearance via the proteasome in cells and brain tissue, in contrast to wild type Hsc70 that stabilized Tau. Thus, DN-Hsc70 mimics the action of small molecule pan Hsp70 inhibitors with regard to Tau metabolism. This shift in Hsc70 function by a single point mutation was the result of a change in the chaperome associated with Hsc70 such that DN-Hsc70 associated more with Hsp90 and DnaJ proteins, whereas wild type Hsc70 was more associated with other Hsp70 isoforms. Thus, isoform-selective targeting of Hsc70 could be a viable therapeutic strategy for tauopathies and possibly lead to new insights in chaperone complex biology.
authors: From the Department of Molecular Medicine, College of Medicine, USF Health Byrd Alzheimer's Institute, University of South Florida, Tampa, Florida 33613, James A. Haley Veteran's Hospital, Tampa, Florida 33612.
authors: Sarah N
authors: SN
authors: Fontaine
authors: Deparment of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, Florida 33620, Institute for Neurodegenerative Disease, University of California, San Francisco, California 94158, and.
authors: Jennifer N
authors: JN
authors: Rauch
authors: From the Department of Molecular Medicine, College of Medicine, USF Health Byrd Alzheimer's Institute, University of South Florida, Tampa, Florida 33613, James A. Haley Veteran's Hospital, Tampa, Florida 33612.
authors: Bryce A
authors: BA
authors: Nordhues
authors: Institute for Neurodegenerative Disease, University of California, San Francisco, California 94158, and.
authors: Victoria A
authors: VA
authors: Assimon
authors: From the Department of Molecular Medicine, College of Medicine, USF Health Byrd Alzheimer's Institute, University of South Florida, Tampa, Florida 33613.
authors: Andrew R
authors: AR
authors: Stothert
authors: Department of Pharmaceutical Science, College of Pharmacy, USF Health Byrd Alzheimer's Institute, University of South Florida, Tampa, Florida 33613.
authors: Umesh K
authors: UK
authors: Jinwal
authors: From the Department of Molecular Medicine, College of Medicine, USF Health Byrd Alzheimer's Institute, University of South Florida, Tampa, Florida 33613, James A. Haley Veteran's Hospital, Tampa, Florida 33612.
authors: Jonathan J
authors: JJ
authors: Sabbagh
authors: Institute for Neurodegenerative Disease, University of California, San Francisco, California 94158, and.
authors: Lyra
authors: L
authors: Chang
authors: Deparment of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, Florida 33620.
authors: Stanley M
authors: SM
authors: Stevens
authors: Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109.
authors: Erik R P
authors: ER
authors: Zuiderweg
authors: Institute for Neurodegenerative Disease, University of California, San Francisco, California 94158, and.
authors: Jason E
authors: JE
authors: Gestwicki
authors: From the Department of Molecular Medicine, College of Medicine, USF Health Byrd Alzheimer's Institute, University of South Florida, Tampa, Florida 33613, James A. Haley Veteran's Hospital, Tampa, Florida 33612, cdickey@health.usf.edu.
authors: Chad A
authors: CA
authors: Dickey
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D015153:Blotting, Western; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D005454:Fluorescence Polarization; D005455:Fluorescent Antibody Technique; D050883:HSC70 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D009154:Mutation / Q000235:genetics; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D016875:tau Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D050883:HSC70 Heat-Shock Proteins; C054369:MAPT protein, human; D020033:Protein Isoforms; D012333:RNA, Messenger; D016875:tau Proteins; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases
keywords: 70-kilodalton heat shock protein (Hsp70); Alzheimer disease; Tau protein (Tau); chaperone; heat shock protein (HSP); inhibitor