Identification of cytoskeletal proteins as binding partners of Bri2 BRICHOS domain

• Proteins must fold into three-dimensional structures to execute their biological functions. Therefore, maintenance of protein homeostasis, proteostasis, including prevention of protein misfolding is essential for cellular activity and health. Molecular chaperones are key actors in proteostasis. BRICHOS domain is an intramolecular chaperone that also interferes with several aggregation-prone proteins including amyloid beta (A beta), involved in Alzheimer's disease (AD). To extend the knowledge about Bri2 BRICHOS interactome we here used recombinant human (rh) Bri2 BRICHOS-mCherry fusion protein to probe for potential binding partners. Firstly, exogenously added Bri2 BRICHOS-mCherry was used to stain brain sections of wildtype and amyloid precursor protein (App) knock-in AD mice exhibiting robust A beta pathology. Unexpectedly, we found that rh Bri2 BRICHOS-mCherry stained the cytoplasm of neurons which are devoid of A beta deposits. To identify these intraneuronal proteins that bind to the rh Bri2 BRICHOS domain, we performed co-immunoprecipitation (co-IP) of mouse brain hippocampi homogenates using the Bri2 BRICHOS-mCherry probe and analyzed co-IP proteins by LC-MS/MS. This identified several cytoskeletal proteins including spectrin alpha and beta chain, drebrin, tubulin beta 3, and beta-actin as binding partners. The interactions were confirmed by a second round of pulldown experiments using rh Bri2 BRICHOS linked to magnetic beads. The interaction of rh Bri2 BRICHOS and tubulin beta 3 was further investigated by staining both mouse brain sections and SH-SY5Y neuroblastoma cells with rh Bri2 BRICHOSmCherry and tubulin beta 3 immunostaining, which revealed partial co-localization. These data suggest a possible interplay of extracellular chaperone Bri2 BRICHOS domain in the intracellular space including the cytoskeleton.

Ämnesord

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Cell- och molekylärbiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Cell and Molecular Biology (hsv//eng)

Nyckelord

Bri2 BRICHOS domain

Amyloid beta

Protein interaction

Cytoskeleton

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