Targeted Suppression of Chaperone-Mediated Autophagy by miR-320a Promotes α-Synuclein Aggregation

Abstract

Chaperone-mediated autophagy (CMA) is involved in wild-type α-synuclein degradation in Parkinson’s disease (PD), and LAMP2A and Hsc 70 have recently been indicated to be deregulated by microRNAs. To recognize the regularory role of miR-320a in CMA and the possible role in α-synuclein degradation, in the present study, we examined the targeting and regulating role of miR-320 in Hsc 70 expression. We first constructed an α-synuclein-overexpressed human neuroblastoma cell line, SH-SY5Y-Syn(+), stably over-expressing wild-type α-synuclein and sensitive to an autophagy inhibitor, which exerted no effect on the expression of LAMP2A and Hsc 70. Then we evaluated the influence on the CMA by miR-320a in the SH-SY5Y-Syn(+) cells. It was shown that miR-320a mimics transfection of specifically targeted Hsc 70 and reduced its expression at both mRNA and protein levels, however, the other key CMA molecule, LAMP2A was not regulated by miR-320a. Further, the reduced Hsc 70 attenuated the α-synuclein degradation in the SH-SY5Y-Syn(+) cells, and induced a significantly high level of α-synuclein accumulation. In conclusion, we demonstrate that miR-320a specifically targeted the 3' UTR of Hsc 70, decreased Hsc 70 expression at both protein and mRNA levels in α-synuclein-over-expressed SH-SY5Y cells, and resulted in significant α-synuclein intracellular accumulation. These results imply that miR-320a might be implicated in the α-synuclein aggravation in PD.

Role of Chaperone-Mediated Autophagy Dysfunctions in the Pathogenesis of Parkinson’s Disease

“…Indeed, the down-regulation of hsc70 and lamp2A in PD brains has been shown to correlate with an up-regulation of six miRNAs targeting the 3′ UTR of hsc70 or lamp2A (Alvarez-Erviti et al, 2013). However, currently there is a dearth of study material regarding the role of “CMA miRNAs” in PD pathogenesis apart from the only one study that showed the up-regulation of one of them resulted in the knock-down of hsc70 and increased levels of asyn in human SH-SY5Y neuroblastoma cells (Li et al, 2014). …”

The N Terminus of Pro-endothelial Monocyte-activating Polypeptide II (EMAP II) Regulates Its Binding with the C Terminus, Arginyl-tRNA Synthetase, and Neurofilament Light Protein

“…It is possible that such a punctate structure can be found in the neurons of these patients. Our data in SH-SY5Y human neuronal cells that have been studied widely as in vitro models of neuronal function and differentiation (44 -46) and in Parkinson disease (47)(48)(49), we show colocalization of 1-70 aa GFP with NFL. This is consistent with reports showing that pro-EMAP II colocalizes and binds with neurofilaments.…”

Role of microRNAs in the Regulation of α-Synuclein Expression: A Systematic Review

“…There are five different studies that report miRNAs that directly impact on proteolytic pathways and result in α-synuclein accumulation (Figure 3; Alvarez-Erviti et al, 2013; Decressac et al, 2013; Li et al, 2014; Zhang and Cheng, 2014; Su et al, 2016). In addition, miR-133b (Niu et al, 2016) and miR-433 (Wang et al, 2008; Schmitt et al, 2012) have been reported to impact on α-synuclein by directly targeting Ras homolog gene family, member A (RhoA) and fibroblast growth factor 20 (FGF20), respectively (Figure 4).…”

“…Therefore, alterations in CMA result in pathological α-synuclein accumulation. Four studies have investigated how miRNA regulation of CMA influences α-synuclein accumulation (Alvarez-Erviti et al, 2013; Li et al, 2014; Zhang and Cheng, 2014; Su et al, 2016). Firstly, Alvarez-Erviti et al (2013) transfected SH-SY5Y cells overexpressing α-synuclein with seven miRNAs that directly bind and negatively regulate two key proteins involved in CMA: Lysosome-associated membrane protein 2 (Lamp2a, hsa-miR-21*; hsa-miR-224; hsa-miR-373*; and hsa-miR-379) and Heat shock protein 70 (Hsc70, hsa-miR-26b: hsa-miR-106a*; and hsa-miR-301b).…”

“…This study also suggested that geniposide had a neuroprotective effect against MPP + /MPTP by inhibiting α-synuclein expression through the miR-21/Lamp2a axis (Su et al, 2016). In relation to Hsc70, two studies added miR-320 (Li et al, 2014) and miR-16-1(Zhang and Cheng, 2014) as direct regulators of Hsc70 expression, which negatively downregulated Hsc70 expression promoting α-synuclein aggregation in SH-SY5Y cells overexpressing α-synuclein, without affecting α-synuclein mRNA levels. Interestingly, miR-16 is a member of the miR-15/107 superfamily, a miRNA family highly dysregulated in Alzheimer’s disease (AD; Parsi et al, 2015).…”