Scientist Stories: Revealing BAG3’s Role in Tau Clearance with Proteintech Antibodies

Written by Hayley Wnuk, PhD, Post-Doctoral Research Associate at the University of Rochester Medical Center

This story is part of the series, #InTheLabWithProteintech, highlighting how Proteintech reagents have supported researchers in advancing their work.

In this article, Hayley Wnuk, PhD, postdoctoral research associate at the University of Rochester highlights a recent Autophagy paper exploring how the regulator BAG3 directs the selective clearance of pathological tau, a key step in the progression of Alzheimer’s disease, and how the authors used Proteintech antibodies to support their mechanistic studies of tau proteostasis.

“BAG3 regulates the specificity of the recognition of specific MAPT species by NBR1 and SQSTM1”, Autophagy (collection 2024; accepted Oct 19, 2023). University of Rochester Medical Center (URMC).

Heng Lin, Sarah Sandkuhler, Colleen Dunlea, Joel Rodwell-Bullock, Darron H King, Gail V W Johnson

The Rundown

Researchers at URMC show that the BAG3 protein acts as a “traffic director” in the brain, assisting in cellular clean-up. BAG3 regulates the clearance of a key protein involved in Alzheimer’s Disease pathogenesis, tau, via selective binding to differential autophagy receptors. BAG3 co-directs singular tau molecules to NBR1, whereas multi-subunit tau tangles are directed towards SQSTM1; ultimately supporting a role for BAG3 in the maintenance of tau proteostasis.

The Big Picture

Our brains are constantly producing and recycling proteins, including tau protein. Although tau plays a crucial role in the maintenance of brain health, improper clearance of structurally modified tau can result in toxic tau build-up. This study explains how our brains direct tau towards the proper clean-up crew, with BAG3 serving as the team leader. This work lends novel insight into cellular mechanisms to boost neuronal homeostasis when faced with Alzheimer’s Disease pathogenesis.

How Proteintech Supported This Research

The following reagents were essential in the detection of key proteins and mechanistic understanding of tau proteostasis in this study:

• BAG3 polyclonal antibody: Used for western blotting and biotinylation for BAG3 affinity assays

• GAPDH polyclonal antibody: Used for western blotting

A Word With The Authors

What inspired you to investigate the role of BAG3 in tau clearance?

"We started studying BAG3 in the context of tau proteostasis a little more than 10 years ago. Earlier studies demonstrated that (1) BAG3 expression is regulated by Hsf-1 which is activated in response to proteotoxic stress, e.g. treatment of cells with a proteasome inhibitor results in a robust upregulation of BAG3 expression,  (2) BAG3 had been shown to facilitate autophagic clearance of other disease relevant, aggregate prone proteins (e.g., mutant SOD1 and mutant huntingtin), and (3) tau can be cleared by autophagy.  Given these previous studies we decided to see if this multidomain/multifunctional protein regulated tau clearance, and the rest is history!"

In your own words, what is the most important take-a-away from this research?

"The tau proteostasis in general, and mechanisms regulating its clearance more specifically, is exquisitely regulated and fine-tuned. Disruption in the expression or localization of these regulatory proteins can contribute to the development of neurodegenerative conditions characterized by the accumulation of disease relevant proteins."

How critical was the BAG3 antibody in uncovering your results?

"The Proteintech BAG3 antibody is used by the majority of investigators in the field.  It is very specific, binding to an epitope in the C-terminal BAG domain of BAG3. It works well on immunoblots, ICC and IHC.  We are very dependent on this antibody for all our BAG3 studies."

How might these findings influence the development of Alzheimer’s Disease therapeutics?

"This is a good question. What the results of these studies suggest is that decreasing the clearance of soluble tau species is likely to be more effective than targeting aggregated forms. Recently there have been studies showing the efficacy of  bifunctional molecules composed of ligands that bind specific clients linked to ligands that target autophagy proteins to clear the client proteins. The results of the findings may help direct the development of the  ligands that are being used to target the complex with the client to the autophagy pathway."

What are your next steps?

"BAG3 not only regulates autophagy, but other vacuolar dependent clearance processes.  Therefore, we are now exploring how BAG3 mediates endocytosis and clearance of exogenous tau. This is because tau pathology has been shown to propagate, i.e., tau can be released and taken up by adjacent cells, but the mechanisms have not been thoroughly delineated.  Although most of our studies have focused on neurons, we are also now examining the role of BAG3 in astrocytes."