Neuroscience Research and Textbook: 3

By Aliasghar Tabatabaei Mohammadi, Shakiba Tolou-Shikhzadeh-Yazdi, Farideh Salimi Bajestani and 9 more

Neuroscience is a fascinating field that explores the inner workings of the brain and nervous system. In this book, readers will delve into the complex world of neuroscience and discover how it relates to human behavior, cognition, and emotion.
Starting with the basics of brain structure and function, the book provides an introduction to the major topics in neuroscience.

• Language: English
• Publisher: Nobel TM
• Release date: Mar 25, 2023
• ISBN: 9791222087061

Book preview

Functional overview of PTEN-induced kinase 1/Parkin dependent mitophagy

When mitochondria are damaged or depolarized, PTEN-induced kinase 1 (PINK1), a mitochondria-localized serine/threonine kinase, stabilizes and accumulates on the outer mitochondrial membrane (OMM). It is present at low levels under baseline settings (Matsuda et al., 2010; Narendra et al., 2010; Rakovic et al., 2010; Vives-Bauza et al., 2010). When PINK1 is in steady state (under normal circumstances), the mitochondrial targeting signal (MTS) directs it to the mitochondria where it traverses the outer mitochondrial membrane (OMM) via the translocase of the OMM 40 (TOM40) and the inner mitochondrial membrane (IMM) via the translocase of the IMM 23 (TIM23) (Wang N. et al., 2020). The MTS's positive charge enables it to go into the matrix, where Mitochondrial Processing Peptidase (MPP) cleaves it (Wang N. et al., 2020). After that, PINK1 is broken down by the ubiquitin proteasome system in the cytoplasm after being released into it by Presenilins-Associated Rhomboid-Like Protein (PARL) in the IMM (Figure 1A; Wang N. et al., 2020). Because the inhibition of either MPP or PARL causes unusually high levels of mitochondrial PINK1 that are sufficient to promote the induction of mitophagy, MPP and PARL perform critical roles in maintaining homeostatic PINK1 localisation (Shi et al., 2011; Greene et al., 2012; Meissner et al., 2015). Failure to completely import PINK1 into the matrix disturbs homeostatic PINK1 processing when mitochondria are injured and/or depolarized, resulting in accumulation and dimerization on the mitochondrial surface (Figure 1A; Sekine et al., 2019; Wang N. et al., 2020). When PINK1 is autophosphorylated by the dimerization at Ser228 and Ser402, it can phosphorylate OMM-associated proteins such Miro, TRAP1, and MFN2 as well as ubiquitin. It can also activate Parkin (Figure 1A; Trempe and Fon, 2013; Aerts et al., 2015; Tanaka, 2020; Wang L. et al., 2020). While proteolytic processing and release of PINK1 from the mitochondrial surface has the opposite effect, buildup of PINK1 on the mitochondrial surface enhances the induction of mitophagy (Shi et al., 2011; Greene et al., 2012; Meissner et al., 2015).

Under normal circumstances, the E3 ubiquitin ligase Parkin sits in the cytosol in a closed and inactive configuration; however, in response to depolarization-induced accumulation of PINK1 on the OMM and its subsequent kinase activity, it is activated and trafficked to the mitochondria (Geisler et al., 2010a; Matsuda et al., 2010; Rakovic et al., 2010; Vives-Bauza et al., 2010; Tang et al., 2017). OMM proteins with phosphorylated ubiquitin chains due to PINK1 activity act as receptors for Parkin recruitment to the mitochondria (Shiba-Fukushima et al., 2014; Okatsu et al., 2015). Parkin changes its conformation to a open intermediate state upon binding to phosphorylated ubiquitin, disrupting the connection between the ubiquitin-like (UBL) and the RING1 domains (Ham et al., 2016; Tanaka, 2020; Wang N. et al., 2020). The fully active version of Parkin results from PINK1-mediated phosphorylation of Ser65 on the UBL, which is readily accessible in this configuration (Shiba-Fukushima et al., 2014; Tang et al., 2017; Tanaka, 2020; Wang N. et al., 2020). Lys6, Lys11, Lys27, Lys48, and Lys63 are the links that ubiquitin chains generate when Parkin is activated (Figure 1B; Geisler et al., 2010a; Bader and Winklhofer, 2020; Tanaka, 2020). As a result of Parkin-driven ubiquitination of OMM proteins, there are more sites for PINK1 phosphorylation, which may subsequently attract additional Parkin, amplifying the PINK1/Parkin signaling process. It has been demonstrated that Parkin ubiquitinates many proteins, including MFN1/2, VDAC1/2/3, Miro, HK1/2, TOMM20, TOMM70A, RHOT1/2, FAF2, and CISD1/2 ( Springer and Macleod, 2016 ; McLelland et al., 2018 ; Bader and Winklhofer, 2020 ).

Mitophagy receptors make sure that damaged mitochondria are recognized and degraded thanks to their ubiquitin-binding domains and their capacity to draw in the cytosolic parts of the autophagy machinery. The sole known mitophagy receptor in yeast is autophagy protein 32 (ATG32), but mammals contain a variety of mitophagy receptors, including NDP52, OPTN, TAX1BP1, NBR1, and -possibly- p62 (Kanki et al., 2009; Wong and Holzbaur, 2014a; Evans and Holzbaur, 2020b; Montava-Garriga and Ganley, 2020). When TBK1 is phosphorylated, the capacity of the NDP52, OPTN, TAX1BP1, and p62 receptors to bind ubiquitin rises, and TBK1 activity is inhibited, autophagosome production is decreased (Moore and Holzbaur, 2016; Bader and Winklhofer, 2020; Evans and Holzbaur, 2020b; Montava-Garriga and Ganley, 2020; Wang L. et al., 2020). Mitophagy receptors have been shown to have LC3-interacting regions (LIR), indicating that they are capable of independently attracting LC3 (Figure 1C). Though mitophagy is still active in cellular systems where the LC3/ATG8 conjugating pathway is inactivated, new research has emphasized the function of ULK1 complex recruitment (Montava-Garriga and Ganley, 2020; Wang L. et al., 2020). FIP200, a component of the ULK1 complex, is directly bound by NDP52, although it is presently unknown if OPTN or TAX1BP1 interact with the ULK1 complex (Montava-Garriga and Ganley, 2020; Wang L. et al., 2020). The various mitophagy receptors work redundantly since OPTN, NDP52, and TAX1BP1 localize to the mitochondria upon depolarization or locally generated ROS on the same timeframe (Moore and Holzbaur, 2016). Nevertheless, unique effects are connected despite the apparent functional commonality. The varied expression of the receptors is linked to specific effects despite the apparent functional overlap. It appears that