The intracellular localization of amyloid β protein precursor (AβPP) intracellular domain associated protein-1 (AIDA-1) is regulated by AβPP and alternative splicing

Abstract

The Amyloid-β Protein Precursor (AβPP) is a widely expressed transmembrane protein that is extensively processed in intracellular vesicular compartments and on the cell membrane. As a result of two sequential proteolytic cleavages, AβPP releases the Amyloid-β (Aβ) peptide, which accumulates in insoluble plaques in the brain of patients affected by Alzheimer's Disease (AD). Another peptide, a C-terminal fragment named AβPP Intracellular Domain (AID), is generated by AβPP processing and is released intracellularly. Several functions for AID have been proposed: pro-apoptotic peptide, regulator of calcium homeostasis, molecule involved in transcriptional regulation. Many intracellular proteins, such as Fe65, Jip-1, Shc, Numb and X11α, interact with AID and modulate its function by different mechanisms. Here we report the cloning and initial characterization of two isoforms of a novel protein that we named AID Associated protein-1a (AIDA-1a), AIDA-1b and AIDA-1b∆Ank. We show that AβPP and the AIDA-1 proteins interact in vitro, in living cells and, endogenously, in leukemia cell lines. Transfected AIDA-1a, AIDA-1b and AIDA-1b∆Ank localize in different compartments and the intracellular distribution of AIDA-1a can be modified by over-expression of AβPP. AIDA-1 proteins are expressed at high levels in the brain; thus, studying their involvement in AβPP processing and AID function might give new insights regarding a possible role for these molecules in normal brain development and in the pathogenesis of AD.

Amyloid-β Protein Precursor (AβPP) Intracellular Domain-associated Protein-1 Proteins Bind to AβPP and Modulate Its Processing in an Isoform-specific Manner

“…Constructs encoding for full-length AIDA-1a, AIDA-1b, and AIDA-1b⌬Ank have been described previously (48). AIDA-1b⌬Ank-2 was cloned by reverse transcription-PCR using total RNA extracted from the pre-B cell line 697 as a template.…”

“…Proteins were purified using glutathione-Sepharose beads according to the Amersham Biosciences protocol. Whole cell lysates from HEK293T cells transfected with different AIDA-1 constructs were incubated with the same amount of GST fusion proteins bound to the beads and used in GST pull-down experiments, as described previously (48).…”

“…These are, for example, X11␣ (33)(34)(35)(36)(37), autosomal recessive hypercholesterolemia (38), Shc (39,40), Growth Factor Receptor-Bound Protein 2 (41), Numb, and Numb-like (28), in addition to the previously mentioned Fe65 (42,43) and Jun N-terminal kinase interacting protein (31, 44 -47). We recently reported the cloning and initial characterization of novel AIDinteracting proteins that we named AID-associated proteins-1 (AIDA-1) (48). Different isoforms of AIDA-1 proteins, deriving from alternative splicing of the same transcript, have been described, and the potential significance of this interaction has been speculated upon but not proved yet.…”

Regulation of the Physiological Function and Metabolism of AβPP by AβPP Binding Proteins

“…AIDA-1a, a shorter splice variant of AIDA-1 composed of two N-terminal SAM domains and a C-terminal PTB domain, binds to APP and decreases secretion of A40 by inhibiting -secretase. In contrast, AIDA-1b, a longer isoform of AIDA-1 with an additional N-terminal region containing ankyrin repeats, does not bind to APP [24,25]. SNX17 is a member of the sorting nexin family that binds low density lipoprotein receptors and regulates the endocytic trafficking of these receptors.…”

“…X11/X11/Mint1, X11-like (X11L)/X11/Mint2, and X11-like2(X11L2)/X11/Mint3 [6,7] [8, 9]; FE65, FE65-like (FE65L1), and FE65-like2 (FE65L2) [6,7,[10][11][12][13]; c-Jun N-terminal kinase (JNK) interacting protein-1b/Islet brain 1 (JIP-1b/IB1) and JIP-2 [14-18]; disabled-1 (Dab1) and Dab2 [19]; ShcA and ShcC [20,21]; Numb and Numb-like (Nbl) [22]; autosomal recessive hypercholesterolemia (ARH) [23]; and APP intracellular domain associated protein-1 (AIDA-1) [24,25]. Some proteins without a PTB domain such as c-Abl [26], growth factor receptor-bound protein 2 (Grb2) [27], UV-DDB [28], and sorting nexin 17 (SNX17) [19] also bind to the GYENPTY motif of APP.…”