RabGEF1/Rabex-5 Regulates TrkA-Mediated Neurite Outgrowth and NMDA-Induced Signaling Activation in NGF-Differentiated PC12 Cells

Abstract

Nerve growth factor (NGF) binds to its cognate receptor TrkA and induces neuronal differentiation by activating distinct downstream signal transduction events. RabGEF1 (also known as Rabex-5) is a guanine nucleotide exchange factor for Rab5, which regulates early endosome fusion and vesicular trafficking in endocytic pathways. Here, we used the antisense (AS) expression approach to induce an NGF-dependent sustained knockdown of RabGEF1 protein expression in stable PC12 transfectants. We show that RabGEF1 is a negative regulator of NGF-induced neurite outgrowth and modulates other cellular and signaling processes that are activated by the interaction of NGF with TrkA receptors, such as cell cycle progression, cessation of proliferation, and activation of NGF-mediated downstream signaling responses. Moreover, RabGEF1 can bind to Rac1, and the activation of Rac1 upon NGF treatment is significantly enhanced in AS transfectants, suggesting that RabGEF1 is a negative regulator of NGF-induced Rac1 activation in PC12 cells. Furthermore, we show that RabGEF1 can also interact with NMDA receptors by binding to the NR2B subunit and its associated binding partner SynGAP, and negatively regulates activation of nitric oxide synthase activity induced by NMDA receptor stimulation in NGF-differentiated PC12 cells. Our data suggest that RabGEF1 is a negative regulator of TrkA-dependent neuronal differentiation and of NMDA receptor-mediated signaling activation in NGF-differentiated PC12 cells.

Cucurbitacin B induces neurogenesis in PC12 cells and protects memory in APP/PS1 mice

“…TrkA could be stimulated by NGF in PC12 cells and lead to the formation of signalling endosomes . Thus, we examined whether the TrkA signalling pathway was taken part in the NGF mimic effect of CuB.…”

“…Similarly, K252a could decrease the neurite length and outgrowth of CuB‐combined NGF group ( P < 0.001). Several signalling cascades initiated by TrkA receptor activation, including the Ras/Raf/ERK pathway, have been implicated in the NGF‐induced differentiation of PC12 cells . Thus, the effect of CuB on the Ras/Raf/ERK signalling pathway was investigated.…”

Endolysosomal Targeting of Mitochondria Is Integral to BAX-Mediated Mitochondrial Permeabilization during Apoptosis Signaling

“…Indeed, while all KD lines were still active in endocytic uptake and trafficking of transferrin, mild alterations were detectable (Figures S5A-S5D). Thus, it is conceivable that colony outgrowth following cellular stress would be differentially impacted by MOMP-independent, distinct roles of Rab5, USP15, and Rabex-5 in cellular survival and proliferation (Homma et al, 2019;Peng et al, 2019;Tam et al, 2015;Zou et al, 2014).…”

Proteomic analysis across patient iPSC-based models and human post-mortem hippocampal tissue reveals early cellular dysfunction, progression, and prion-like spread of Alzheimer’s disease pathogenesis

“…While only three Rab proteins were dysregulated in ADHS, 16 members of the Rab superfamily were altered in ADHG and 6 in ADHPMBT. Among them, RABGEF1, a guanine nucleotide exchange factor for RAB5 [28], a key regulator of endosome fusion and trafficking [26, 29], was elevated in both ADHG and ADHPMBT. Interestingly, two isoforms of RAB5, RAB5A and RAB5C were increased only in ADHG.…”