Autophagy and apoptosis dysfunction in neurodegenerative disorders

Abstract

Autophagy and apoptosis are basic physiologic processes contributing to the maintenance of cellular homeostasis. Autophagy encompasses pathways that target long-lived cytosolic proteins and damaged organelles. It involves a sequential set of events including double membrane formation, elongation, vesicle maturation and finally delivery of the targeted materials to the lysosome. Apoptotic cell death is best described through its morphology. It is characterized by cell rounding, membrane blebbing, cytoskeletal collapse, cytoplasmic condensation, and fragmentation, nuclear pyknosis, chromatin condensation/fragmentation, and formation of membrane-enveloped apoptotic bodies, that are rapidly phagocytosed by macrophages or neighboring cells. Neurodegenerative disorders are becoming increasingly prevalent, especially in the Western societies, with larger percentage of members living to an older age. They have to be seen not only as a health problem, but since they are care-intensive, they also carry a significant economic burden. Deregulation of autophagy plays a pivotal role in the etiology and/or progress of many of these diseases. Herein, we briefly review the latest findings that indicate the involvement of autophagy in neurodegenerative diseases. We provide a brief introduction to autophagy and apoptosis pathways focusing on the role of mitochondria and lysosomes. We then briefly highlight pathophysiology of common neurodegenerative disorders like Alzheimer's diseases, Parkinson's disease, Huntington's disease and Amyotrophic lateral sclerosis. Then, we describe functions of autophagy and apoptosis in brain homeostasis, especially in the context of the aforementioned disorders. Finally, we discuss different ways that autophagy and apoptosis modulation may be employed for therapeutic intervention during the maintenance of neurodegenerative disorders.

Keywords: AD; AIF; ALS; AMBRA; AMP-activated protein kinase; AMPA; AMPK; APP; ATG; Alzheimer's diseases; Apo-E; Aβ; BDNF; CMA; ER; ESCRT; HD; HEK293; HIP-1; Htt; Huntingtin interacting protein; Huntingtin protein; Huntington's disease; InsP(6)Ks; LAMP; LC3; LRPPRC; MAP15; Mitochondria dysfunction; N-methyl-d-aspartate; NCCD; NMDA; PCD; PD; PINK-1; PON 1–3; PTEN-induced putative kinase 1; Parkinson's disease; Porteopathies; RCAN-1; RSVA314; RSVA405; RUBICON; RUN domain and cysteine rich domain containing; Resveratrol; TAR DNA-binding protein 43kDa; TDP-43-kDa; Trehalose; UPS; UVRAG; VCP; X-box binding protein-1; XBP-1; activating molecule in Beclin-1-regulated autophagy; alpha-synuclein; amyloid beta precursor protein; amyloid-beta; amyotrophic lateral sclerosis; apolipo-protein E; apoptosis-inducing factor; autophagosome-associated light chain 3; autphagy related genes; brain-derived neurotrophic factor; chaperon-mediated autophagy; endoplasmic reticulum; endosomal sorting complexes required for transport; human embryonic kidney 293 cells; inositol hexakisphosphate kinases; lysosomal associated membrane proteins; mHtt; mPTP; mTOR; mammalian target of rapamycin; microtubule-associated protein 15; mitochondrial permeability transition pore; mitochondrion-associated leucine-rich PPR-motif containing protein; mutant Huntingtin protein; nomenclature committee on cell death; p53; pQ; paraxonase enzymes; poly-glutamine; programmed cell death; regulator of calcineurin-1; tumor protein 53; ubiquitin-proteasome system; ultra-violet radiation resistance-associated gene; valosin-containing protein; α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid; α-syn.