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RIN3 Binds to BIN1 and CD2AP to increase APP‐CTFS in early endosomes
Author(s) -
Shen Ruinan,
Wu Chengbiao
Publication year - 2020
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1002/alz.047161
Subject(s) - biology , microbiology and biotechnology , basal forebrain , endocytic cycle , endosome , guanine nucleotide exchange factor , cholinergic , hippocampal formation , cholinergic neuron , olfactory bulb , rab , gtpase , neuroscience , genetics , cell , central nervous system , intracellular , endocytosis
Background About one‐third of the genes related to Alzheimer’s disease (AD) identified by GWAS encode proteins that function predominantly in the endocytic pathways. Among them, the Ras and Rab Interactor 3, RIN3 is a guanine nucleotide exchange factors (GEFs) for the Rab5 small GTPase family and has been implicated to be a risk factor for both late onset AD (LOAD) and sporadic early onset AD (sEOAD). However, how RIN3 is linked to AD pathogenesis is currently undefined. Methods Quantitative PCR and immunoblotting were used to measure gene expression levels in mouse brain, cultured basal forebrain cholinergic neuron (BFCNs) or PC12 cells. Immunostaining was used to define subcellular localization of RIN3 and visualize endosomal changes in cultured primary BFCNs and PC12 cells. Recombination RIN3‐flag‐tagged protein was purified from HEK293T cells and was used to define RIN3‐interactomes by mass spectrometry. Live imaging of primary neurons was used to examine axonal transport. Results Expression of RIN3 was upregulated in the brain tissues of young APP/PS1 mice. The increase was specific for the hippocampus and cortex since RIN3 expression level did not show an increase in either the olfactory bulb or the cerebellum. RIN3 mRNA level was also found to be elevated in embryonic day (E18) 18 in primary basal forebrain cholinergic neurons (BFCNs) cultured from APP/PS1 mouse. Concomitant early endosome enlargement was seen in these BFCNs. We have demonstrated that RIN3 interacted with two other AD risk factors: BIN1(bridging integrator 1) and CD2AP (CD2 associated protein). Both BIN1 and CD2AP were recruited to early endosomes through binding to the proline rich domain (PRD) of RIN3. Overexpression of RIN3 or CD2AP promoted APP cleavage to increase APP carboxyl terminal fragments (CTFs) in PC12 cells, while upregulating RIN3 or BIN1 neuronal isoform increase phosphorylated Tau level. The effect of upregulation of RIN3 expression to increase APP CTFs was ameliorated by a dominant negative Rab5 construct (Rab5 S34N ). Increased expression of RIN3 impaired axonal trafficking of both APP and BACE1. Conclusion RIN3 is significantly unregulated and correlated with endosomal dysfunction in APP/PS1 mouse. Through interacting with BIN1 and CD2AP, increased RIN3 expression alters axonal trafficking and procession of APP.