Phosphatidylserine Synthase Manipulation in Glial Subtypes: Analysis of Parkinson’s Disease-Like Pathology and Physiological Changes = 신경교세포 하위 유형별 포스파티딜세린 합성효소 조절: 파킨슨병에 대한 이해

다국어 초록 (Multilingual Abstract)

Phosphatidylserine synthase (PSS) plays a critical role in maintaining central nervous system (CNS) function and organismal homeostasis by regulating phospholipid synthesis. Dysregulation of Pss activity, particularly in glial cells, has been implicated in neurodegenerative disorders such as Parkinson’s disease (PD). In this study, we ex-amined the subtype-specific roles of Pss in Drosophila glial cells and their impact on CNS integrity, neurodevelopment, and aging. Cortex glia-specific knockdown of Pss led to reduced dopaminergic neuron numbers in PPL1 and PPL2 clusters, impaired locomotion, shortened lifespan. These phenotypes were accompanied by increased oxidative stress, as demonstrated by elevated reactive oxygen species (ROS) levels detected via dihydroethidium (DHE) staining. Further analysis using mitoSOX revealed region-specific ROS accumulation in the PPL1 cluster. Mechanistically, Pss knockdown is presumed to reduce phosphatidylserine (PS) levels, a lipid known to facilitate AKT acti-vation. This likely led to decreased levels of phosphorylated AKT (pAKT). Reduced pAKT levels were associated with downregulation of mitochondrial transcription factor A (Tfam), resulting in apoptosis and neuronal death. Similarly, Pss dysregulation in midline glia caused severe developmental defects, including pupal lethality, while Pss knockdown or overexpression in astrocytes led to significant lifespan reductions, motor impairments, and neurodegenerative phe-notypes characterized by vacuolization. These findings underscore the essential role of Pss in glial cell subtypes, emphasizing its im-portance in CNS development, aging, and the progression of neuro-degenerative diseases. Future research targeting Pss pathways may provide therapeutic strategies for mitigating neurodegenerative con-ditions and enhancing CNS health.

국문 초록 (Abstract)

포스파티딜세린 합성효소(PSS)는 인지질 합성을 조절하여 중추신경계 기능과 생체 내 항상성을 유지하는 데 중요한 역할을 합니다. 특히, Pss 활성의 조절 이상은 파킨슨병과 같은 신경퇴행성 질환과 관련이 있는 것으로 나타났습니다. 본 연구에서는 초파리의 신경교세포에서 Pss의 역할과 신경 발달, 노화에 미치는 영향을 조사했습니다. Cortex glia에서 Pss를 특이적으로 억제한 결과, PPL1 및 PPL2 클러스터의 도파민성 뉴런 수가 감소했으며, 운동 기능 저하, 수명 단축, 미토콘드리아 기능 장애로 인한 활성산소 수준의 증가가 관찰되었습니다. 또한, 미토콘드리아 전사 인자 A(Tfam)의 발현이 감소하여 세포 사멸이 유발되었습니다. 마찬가지로, midline glia에서 Pss 조절 이상은 번데기 치사율 증가와 같은 심각한 발달 결함을 초래했으며, 성상세포에서의 Pss 억제 또는 과발현은 수명 단축, 운동 기능 저하, 공포화(vacuolization)로 특징지어지는 신경퇴행성 표현형을 유발했습니다. 이러한 결과는 신경교세포 각 타입에서 Pss의 필수적인 역할을 강조하며, 신경계 발달, 노화, 신경퇴행성 질환 진행에서의 중요성을 보여줍니다.

목차 (Table of Contents)

• 1. Introduction 1
• 1.1. Glia 1
• 1.1.1. The importance of Glia in the nervous system 1
• 1.1.2. Diversity of Glia in mammal 2
• 1.1.2.1. Astrocyte 3
• 1.1.2.2. Microglia 4
• 1.1.3. Diversity of Glia in Drosophila 6
• 1.1.3.1. Astrocyte-like glia 7
• 1.1.3.2. Cortex glia 9
• 1.2. Phosphatidylserine (PS) 11
• 1.2.1. The importance of Phosphatidylserine 11
• 1.2.2. Phosphatidylserine and nervous system 11
• 1.2.3. Phosphatidylserine Biosynthesis 12
• 1.2.3.1. Mechanism of Phosphatidylserine Biosynthesis 12
• 1.2.3.2. Sources of Serine 13
• 1.2.3.3. Intracellular phosphatidylserine transport 13
• 1.2.3.4. Phosphatidylserine synthase 14
• 1.2.3.4.1. Structural characteristics of PSS 14
• 1.2.3.4.1.1. Functional Role of PSS1 15
• 1.2.3.4.1.2. Functional Role of PSS2 15
• 1.2.3.4.2. PSS Research in Model Organisms 16
• 1.2.3.4.2.1. PSS research in yeast 17
• 1.2.3.4.2.2. PSS research in C. elegans 17
• 1.2.3.4.2.3. PSS research in Drosophila 18
• 1.2.3.4.2.4. PSS research in mice 19
• 1.3. Parkinson's Disease 20
• 1.3.1. Astrocyte and Parkinson's Disease 21
• 1.3.2. Microglia and Parkinson's Disease 22
• 1.3.3. Mitochondria in Parkinson's Disease 23
• 1.4. Aims of the Study 24
• 2. Materials and Methods 25
• 2.1. Drosophila genetics and strains 25
• 2.2. Reverse transcription quantitative real-time PCR 25
• 2.3. Western blotting 26
• 2.4. Immunochemistry staining 27
• 2.5. Life span 27
• 2.6. Climbing ability 27
• 2.7. Brain histology 28
• 2.8. Detection of ROS in brain tissue 28
• 2.9. Mitochondrial ROS detection in brain 28
• 2.10. Cell death analysis 29
• 2.11. Statistical analysis 29
• 3. Results 30
• 3.1. Knockdown of Pss gene in cortex glia decreases lifespan and motor ability 30
• 3.2. Knockdown of Pss gene in cortex glia induces cell death in a head 34
• 3.3. Knockdown of Pss gene in cortex glia induces dopaminergic neuronal cell death 35
• 3.4. Knockdown of Pss gene in cortex glia results in mitochondrial dysfunction 38
• 3.5. Knockdown of Pss gene in cortex glia results in mitochondrial ROS 42
• 3.6. Knockdown of Pss suppresses AKT signaling in cortex glia 45
• 3.7. Regulation of Pss gene in subperineurial glia, astrocytes, wrapping glia, and midline glia also decreases lifespan 47
• 3.8. Regulation of Pss gene in astrocytes decreases lifespan and motor ability 51
• 3.9. Knockdown of Pss gene in astrocytes induces vacuolization in a head 54
• 4. Discussion 56