Understanding Golgi Fragmentation in Amyotrophic Lateral Sclerosis Lecture -L4 PDF

Molecular Medicine Golgi Apparatus and Disease Dr Temba Mudariki  Learning Outcomes-Background Explain how proteins move from the ER to the Golgi Integrate the principles of molecular events in relation to the initiation or development of pathophysiologic...

Molecular Medicine Golgi Apparatus and Disease Dr Temba Mudariki  Learning Outcomes-Background Explain how proteins move from the ER to the Golgi Integrate the principles of molecular events in relation to the initiation or development of pathophysiological changes in the Golgi Apparatus Apply appropriate molecular technologies in translational research  Overview Introduction Golgi Apparatus Structure and function Overview of ALS as a neurodegenerative disease targeting motor neurons The Golgi Apparatus in Neurons Fragmentation of the Golgi Apparatus Amyotrophic Lateral Sclerosis  Overview Golgi Fragmentation in ALS Impairment of Cellular Trafficking as a Trigger for Golgi Fragmentation in ALS Golgi Fragmentation and Autophagy Dysfunction in ALS Golgi Fragmentation and Axonal Homeostasis  Learning Outcomes 1. Understand the role of the Golgi apparatus in maintaining cellular homeostasis and its importance in neuronal cells. 2. Explore the pathological mechanisms of Golgi fragmentation in ALS and its potential implications in the progression of the disease. 3. Discuss the potential links between Golgi fragmentation, defects in cellular trafficking, ER stress, autophagy dysfunction, and axonal degeneration in the context of ALS. 4. Recognize the potential impact of Golgi fragmentation on the broader understanding of neurodegenerative disorders.  Golgi apparatus Processing and sorting hub Transport and targeting of soluble cargo proteins and lipids Central role – secretory pathway Structure and function – alterations affect homeostasis of cellular proteins and lipids Structural and functional changes – linked to many diseases ✓Neurodegenerative diseases ✓Ischemic stroke ✓Cardiovascular diseases ✓Pulmonary arterial hypertension ✓Infectious diseases and cancer  Golgi apparatus structure and function Camillio Golgi (1898) – described the Golgi apparatus Characterisation – cisternal membrane structures forming Golgi stack, surrounded by vesicles Distribution- based on resident proteins Divided into 3 regions- cis, medial and trans-Golgi cisternae Vertebrate cells – Golgi stacks are laterally interconnected by tubular membranes –Golgi ribbon Golgi ribbon structure is supported by Golgi matrix Golgi matrix – dynamic structural proteins- integrity and vesicular trafficking  Golgi apparatus structure and function Golgi apparatus – two main function 1. Posttranslational protein modification –glycan processing throughout Golgi stacks 2. Sorting, Packing, Routing, and recycling-modified cargo to appropriate cellular destinations Main secretory pathway steps; ❖Newly synthesized proteins or lipids enter exit sites of ER and sorted into budding vesicles dependent on the COPII. ❖Vesicles move to ER-Golgi intermediate compartment (ERGIC) and forward to cis-Golgi networks (CGN)  Golgi apparatus structure and function ❖Proteins or lipids enter cis-Golgi cisternae and move towards the trans-Golgi cisternae. ✓Vesicular transport model – Golgi cisternae are static; cargo are transported through them by COPI vesicles ✓Cisternal maturation model- cisternae are dynamic structures, while Golgi enzymes are recycled via retrograde transport of COPI vesicles. ❖Vesicles reach trans-Golgi network (TGN)- sorting of products to their final destination –lysosomes, endosomes, or plasma membrane Overview of ALS as a neurodegenerative disease targeting motor neurons Aetiology and Pathophysiology Clinical Manifestations Aspects of Disease Progression Pathological Hallmarks 5-10% of cases being familial (inherited) https://doi.org/10.1016/j.cell.2022.12.032  Overview of ALS as a neurodegenerative disease targeting motor neurons Diagnosis and Management Impact on Patients and Families Research and Therapeutic Challenges  The Golgi Apparatus in Neurons Golgi in Neurons Golgi in Axons Golgi in Dendrites  The Golgi Apparatus in Neurons Golgi in Neurons Golgi in Axons Golgi in Dendrites  Significance of Golgi Outposts in Local Secretory Trafficking within Neurites Neurites Golgi Outposts Local Secretory Trafficking Significance of Golgi Outposts in Neurites Secretory pathways and satellite organelles in neuronal dendrites  Relationship between Axonal Transport and Golgi Function in Neurons ❖Introduction ❖Axonal Transport Overview ❖Golgi Function in Neurons ❖Relationship between Axonal Transport and Golgi Function  Fragmentation of the Golgi Apparatus Normal Morphological Characteristics Capacity for Profound Changes  Reversible and Irreversible Golgi Fragmentation Reversible Golgi Fragmentation Irreversible Golgi Fragmentation Pathological Significance  Golgi Fragmentation and Neurodegenerative Diseases A B  Evidence Linking Golgi Fragmentation to Neurodegenerative Diseases, including ALS Research Studies ALS and Golgi Fragmentation Impaired Protein Trafficking Cellular Stress and Golgi Fragmentation  A. RNA Dysfunction B. Brain ALS Brain Scan Amyotrophic Lateral Sclerosis (ALS) ❖Introduction ❖Aetiology of ALS  Pathological Hallmarks of ALS: Accumulation of Misfolded Protein Aggregates Introduction Pathological Hallmarks Cytoplasmic inclusions and nuclear abnormalities Consequences of Protein Aggregate Accumulation TDP-43 and SOD1  Golgi Fragmentation in ALS ▪ Evidence of Golgi Fragmentation in ALS ▪ Presence in Patient Motor Neurons ▪ Animal and Cellular Disease Models ▪ Association with Specific ALS-Linked Mutations ▪ Vulnerability of Larger Human Motor Neurons ▪ Implications for Disease Pathogenesis ▪ Therapeutic Implications Research has shown an association between Golgi fragmentation and specific ALS-linked mutations- SOD1, TDP-43, FUS, and C9orf72 TDP-43 is involved in RNA processing and protein homeostasis  Impairment of Cellular Trafficking as a Trigger for Golgi Fragmentation in ALS Sensitivity of ER-Golgi Compartments Implications on Cellular Homeostasis Evidence Linking Impairment to Golgi Fragmentation Specific Mechanisms in ALS Mutant Proteins Disruption of Protein Sorting and Processing Overall Impact on Cellular Function Therapeutic Implications  Golgi Fragmentation and Autophagy Dysfunction in ALS: Role of the Golgi in Autophagosome Biogenesis Potential Implications of Golgi Fragmentation on Autophagy Dysfunction Relationship Between Golgi Fragmentation and Autophagy Regulation Highlighting Contradictory Observations Potential Pathological Links in ALS Therapeutic Implications  Golgi Fragmentation and Axonal Homeostasis: Specialized Role of the Golgi in Maintaining Axonal Homeostasis Impact on Synaptic Plasticity Potential Impact of Golgi Fragmentation on Axonal Functions Relevance to ALS-Related Axonal Degeneration Implications for Axonal Transport Potential Impact on Synaptic Dysfunction Therapeutic Implications  Case History Case History 1: Familial ALS Patient Background: ❖ Name: Sarah Thompson ❖ Age: 45 ❖ Family History: Sarah's mother was diagnosed with ALS in her early 50s. No other significant family medical history.  Initial Symptoms and Workout: Sarah, a marketing executive, began experiencing muscle weakness and occasional tripping, which she initially attributed to stress and overwork. She noticed that her grip strength was diminishing, and she struggled with tasks such as lifting objects and typing for prolonged periods.  Medical Evaluation and Diagnosis Sarah sought medical attention and underwent a thorough neurological examination, which revealed signs of muscle atrophy and reduced muscle strength, particularly in the upper limbs. Electromyography (EMG) and genetic testing were performed. EMG showed signs of denervation and reinnervation, consistent with ALS. Genetic testing revealed a mutation in the SOD1 gene, a known familial ALS-associated gene. Additional tests, including nerve conduction studies and MRI, were conducted to confirm the diagnosis and rule out other potential causes of weakness and muscle atrophy.  Confirmation of Familial ALS Genetic testing confirmed the presence of an ALS-associated mutation in the SOD1 gene, which, combined with the clinical symptoms and EMG findings, supported the diagnosis of familial ALS in Sarah. Consultation with a genetic counsellor provided further information about the inheritance pattern of the disease and implications for Sarah's family members.  Treatment and Management Plan Sarah's treatment plan included riluzole, the only FDA-approved medication for ALS, to slow the progression of the disease. Given the familial nature of Sarah's ALS, family members were offered genetic counselling and testing to assess their risk of carrying the mutation. Sarah was referred to a multidisciplinary ALS clinic, where she received comprehensive care and support, including physical therapy, occupational therapy, and assistive devices to manage her symptoms.  Long-Term Management and Support Sarah's care plan involved ongoing monitoring and adjustments to her management plan as the disease progressed. The clinic provided support and resources for Sarah's family members, helping them understand the genetic implications and providing emotional support.  Case History 2: Sporadic ALS Patient Background: Name: James Miller Age: 50 Medical History: No significant medical history or family history of neurodegenerative disorders.  Initial Symptoms and Workout James, a teacher, began experiencing muscle weakness, particularly in his legs, which led to frequent stumbling and difficulty climbing stairs. He noticed muscle twitching and cramping, particularly in his arms and legs, and reported increasing difficulty with fine motor tasks such as writing and buttoning his shirt.  Medical Evaluation and Diagnosis James underwent a comprehensive neurological examination, which revealed signs of muscle weakness, atrophy, and fasciculations, particularly in the limbs. Electromyography (EMG) and nerve conduction studies were performed, showing evidence of denervation and reinnervation consistent with ALS. MRI was conducted to rule out other potential causes of symptoms.  Confirmation of Sporadic ALS The combination of clinical symptoms, EMG findings, and neuroimaging results led to the diagnosis of sporadic ALS in James. Further blood tests were performed to rule out other potential causes of symptoms, including metabolic and autoimmune disorders.  Treatment and Management Plan Upon diagnosis, James was prescribed riluzole to help slow the progression of the disease and manage his symptoms. He was referred to a multidisciplinary ALS clinic, where he received comprehensive care, including physical therapy and assistive devices to support his mobility.  Long-Term Management and Support James's care plan involved ongoing monitoring and adjustments to his management plan as the disease progressed. The clinic provided emotional support and resources to help James and his family cope with the challenges associated with a diagnosis of sporadic ALS.  Summary Role of the Golgi in Cellular Homeostasis Significance of Golgi Fragmentation in ALS Implications for Disease Progression Therapeutic Implications Complex Interplay of Cellular Mechanisms Importance for Future Research and Interventions  Recommended Reading 1. Research Articles: 1. "Golgi fragmentation in amyotrophic lateral sclerosis, an overview of possible triggers and consequences" by Jos H. T. M. Koopman et al. (Neuroscience & Biobehavioral Reviews, 2016) 2. "Golgi Fragmentation in Amyotrophic Lateral Sclerosis, a role for the Golgi apparatus in stress granule formation" by Nils Halberg et al. (Neurobiology of Disease, 2018) 2. Review Articles: 1. "Golgi fragmentation in amyotrophic lateral sclerosis, Mechanisms and Potential Therapeutic Targets" by Brittany A. Allen and Daniel K. Nomura (Neurotherapeutics, 2020) 3. Book Chapters: 1. "The Golgi apparatus and the centrosome" by Graham Warren, Jennifer Lippincott-Schwartz, and Stephen L. Scherer in "The Neuronal Cytoskeleton, Motor Proteins, and Organelle Trafficking in the Axon" (2016) 4. Scientific Reviews: 1. "Golgi structure and function in health and disease" by Kathryn R. Ayscough et al. (Biology of the Cell, 2018) 2. "Golgi in the Nervous System" by Peter G. H. Clarke and Robert D. Burgoyne (Current Opinion in Cell Biology, 1998) 5. Research Journals: 1. Journals such as "Cell", "Neuron", "Nature Cell Biology", and "Journal of Cell Science" often publish articles and reviews related to Golgi fragmentation, cellular trafficking, and neurodegenerative diseases. End of Session