Unbiased proteomic profiling reveals the IP3R modulator AHCYL1/IRBIT as a novel interactor of microtubule-associated protein tau

Lena Wischhof,Aasha Adhikari,Mrityunjoy Mondal,Anaïs Marsal-Cots,Jacek Biernat,Eva Maria Mandelkow,Eckhard Mandelkow,Dan Ehninger,Pierluigi Nicotera,Daniele Bano

doi:10.1016/j.jbc.2022.101774

Abstract

Microtubule-associated protein tau is a naturally unfolded protein that can modulate a vast array of physiological processes through direct or indirect binding with molecular partners. Aberrant tau homeostasis has been implicated in the pathogenesis of several neurodegenerative disorders, including Alzheimer’s disease. In this study, we performed an unbiased high-content protein profiling assay by incubating recombinant human tau on microarrays containing thousands of human polypeptides. Among the putative tau-binding partners, we identify SAH hydrolase–like protein 1/inositol 1,4,5-trisphosphate receptor (IP3R)–binding protein (AHCYL1/IRBIT), a member of the SAH hydrolase family and a previously described modulator of IP3R activity. Using coimmunoprecipitation assays, we show that endogenous as well as overexpressed tau can physically interact with AHCYL1/IRBIT in brain tissues and cultured cells. Proximity ligation assay experiments demonstrate that tau overexpression may modify the close localization of AHCYL1/IRBIT to IP3R at the endoplasmic reticulum. Together, our experimental evidence indicates that tau interacts with AHCYL1/IRBIT and potentially modulates AHCYL1/IRBIT function.

Highlights

Microtubule-associated protein (MAP) tau (MAPT) is a highly soluble and natively unfolded molecule that normally binds microtubules and contributes to regulation axonal transport in neurons [1,2,3]
We focused our Journal Pre-proof study on AHCYL1/IRBIT, a protein that modulates IP3R activity [42,43,44] and with a potential role in mitochondrial bioenergetics that may be relevant in tauopathies as recently emphasized [41]
It is known that the C-terminal region of AHCYL1/IRBIT is highly homologous to the adenosylhomocysteinase adenosylhomocysteine hydrolase (AHCY), whereas the N-terminal region is unique for the IRBIT-family members across phyla [44,45]

Summary

Introduction

Microtubule-associated protein (MAP) tau (MAPT) is a highly soluble and natively unfolded molecule that normally binds microtubules and contributes to regulation axonal transport in neurons [1,2,3]. Using 50 ng and 5 ng of E. coli-derived recombinant human full-length tau protein [36], we detected 124 polypeptides that interact with htau40 in our experimental conditions (Figure 1 and Table S1). These data show that tau physically interacts with AHCYL1/IRBIT in transiently transfected HEK293T cells.

Results

Conclusion