ABSTRACT
A hallmark of aging is loss of differentiated cell identity. Aged Drosophila midgut differentiated enterocytes (ECs) lose their identity, impairing tissue homeostasis. To discover identity regulators, we performed an RNAi screen targeting ubiquitin-related genes in ECs. Seventeen genes were identified, including the deubiquitinase Non-stop (CG4166). Lineage tracing established that acute loss of Non-stop in young ECs phenocopies aged ECs at cellular and tissue levels. Proteomic analysis unveiled that Non-stop maintains identity as part of a Non-stop identity complex (NIC) containing E(y)2, Sgf11, Cp190, (Mod) mdg4, and Nup98. Non-stop ensured chromatin accessibility, maintaining the EC-gene signature, and protected NIC subunit stability. Upon aging, the levels of Non-stop and NIC subunits declined, distorting the unique organization of the EC nucleus. Maintaining youthful levels of Non-stop in wildtype aged ECs safeguards NIC subunits, nuclear organization, and suppressed aging phenotypes. Thus, Non-stop and NIC, supervise EC identity and protects from premature aging.
Subject(s)
Aging, Premature/genetics , Aging/genetics , Drosophila Proteins/genetics , Drosophila melanogaster/physiology , Enterocytes/physiology , Animals , Disease Models, Animal , Drosophila Proteins/metabolism , Female , Male , Phenotype , ProteomeABSTRACT
Skp1, a component of the ubiquitin E3 ligases, was found to be decreased in the brains of sporadic Parkinson's disease (PD) patients, and its overexpression prevented death of murine neurons in culture. Here we expose the neuroprotective role of the Drosophila skp1 homolog, skpA, in the adult brain. Neuronal knockdown of skpA leads to accumulation of ubiquitinated protein aggregates and loss of dopaminergic neurons accompanied by motor dysfunction and reduced lifespan. Conversely, neuronal overexpression of skpA reduces aggregate load, improves age-related motor decline, and prolongs lifespan. Moreover, SkpA rescues neurodegeneration in a Drosophila model of PD. We also show that a Drosophila homolog of FBXO7, the F Box protein, Nutcracker (Ntc), works in the same pathway with SkpA. However, skpA overexpression rescues ntc knockdown phenotype, suggesting that SkpA interacts with additional F box proteins in the adult brain neurons. Collectively, our study discloses Skp1/SkpA as a potential therapeutic target in neurodegenerative diseases.
ABSTRACT
Glial phagocytosis is critical for the development and maintenance of the CNS in vertebrates and flies and relies on the function of phagocytic receptors to remove apoptotic cells and debris. Glial phagocytic ability declines with age, which correlates with neuronal dysfunction, suggesting that increased glial phagocytosis may prevent neurodegeneration. Contradicting this hypothesis, we provide experimental evidence showing that an elevated expression of the phagocytic receptors Six-Microns-Under (SIMU) and Draper (Drpr) in adult Drosophila glia leads to a loss of both dopaminergic and GABAergic neurons, accompanied by motor dysfunction and a shortened lifespan. Importantly, this reduction in neuronal number is not linked to neuronal apoptosis, but rather to phosphatidylserine-mediated phagoptosis of live neurons by hyper-phagocytic glia. Altogether, our study reveals that the level of glial phagocytic receptors must be tightly regulated for proper brain function and that neurodegeneration occurs not only by defective, but also excessive glial cell function.
Subject(s)
Dopaminergic Neurons/physiology , Drosophila Proteins/metabolism , Drosophila/metabolism , GABAergic Neurons/physiology , Membrane Proteins/metabolism , Neuroglia/metabolism , Phagocytosis/genetics , Animals , Apoptosis/genetics , Apoptosis/physiology , Brain/cytology , Brain/metabolism , Brain/pathology , Drosophila/genetics , Drosophila/physiology , Drosophila Proteins/genetics , Longevity/genetics , Longevity/physiology , Membrane Proteins/genetics , Motor Disorders/genetics , Motor Disorders/metabolism , Nervous System Malformations/genetics , Nervous System Malformations/metabolism , Neuroglia/cytology , Neuroglia/pathology , Phagocytosis/physiology , Phosphatidylserines/metabolismABSTRACT
The inability of differentiated cells to maintain their identity is a hallmark of age-related diseases. We found that the transcription factor Hey supervises the identity of differentiated enterocytes (ECs) in the adult Drosophila midgut. Lineage tracing established that Hey-deficient ECs are unable to maintain their unique nuclear organization and identity. To supervise cell identity, Hey determines the expression of nuclear lamins, switching from a stem-cell lamin configuration to a differentiated lamin configuration. Moreover, continued Hey expression is required to conserve large-scale nuclear organization. During aging, Hey levels decline, and EC identity and gut homeostasis are impaired, including pathological reprograming and compromised gut integrity. These phenotypes are highly similar to those observed upon acute targeting of Hey or perturbation of lamin expression in ECs in young adults. Indeed, aging phenotypes were suppressed by continued expression of Hey in ECs, suggesting that a Hey-lamin network safeguards nuclear organization and differentiated cell identity.
