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Activation of a novel microglial gene encoding a lysosomal membrane protein in response to neuronal apoptosis
M Origasa1, S Tanaka, K Suzuki
1Molecular Neurobiology Laboratory, Division of Biological Science, Graduate School of Science, Hokkaido University, North Ward N10 W8, Sapporo 060-0810, Japan.
Abstract:
In an attempt to understand the molecular mechanism of microglial activation in response to neuronal death or degeneration, we have employed cerebellar cell cultures prepared from P7 rats and grown in normal K(+) (5.4 mM) medium. Under this condition, glial cells respond to degeneration and cell death of granule neurons that begins to occur at 4 days in vitro (DIV). Here we describe a novel gene, granule cell death-10 (gcd-10) that is expressed in microglia and up-regulated in an early period of granule cell death. gcd-10 is homologous to the mouse lysosomal-associated multispanning membrane protein (LAPTm5) with hematopoietic origin. Immunocytochemistry and vital staining with acridine orange revealed that GCD-10 was localized at the perinuclear area of cultured microglia and COS 1 cells infected with a GCD-10-expressing adenoviral vector. In cerebellar cell cultures, however, GCD-10 was markedly up-regulated and widely distributed to the cytoplasm, which paralleled the localization of the ED1 antigen, the lysosomal marker. In vivo, gcd-10 is expressed mainly in the brain and the spleen, and was up-regulated upon nerve injury in retina 7 days after optic nerve transection. These findings suggest that gcd-10 is involved in the dynamics of lysosomal membranes associated with microglial activation both in vitro and in vivo.
Insights
Researchers identified a novel gene, granule cell death-10 (gcd-10), in microglia that is upregulated during neuronal degeneration. GCD-10 appears to be involved in lysosomal membrane dynamics during microglial activation in the brain and spleen.
Area of Science:
- Neuroscience
- Immunology
- Molecular Biology
Background:
- Microglial activation is crucial for responding to neuronal damage.
- The molecular mechanisms underlying microglial responses to neuronal death are not fully understood.
Purpose of the Study:
- To investigate the molecular mechanisms of microglial activation in response to neuronal degeneration.
- To identify novel genes involved in this process.
Main Methods:
- Utilized P7 rat cerebellar cell cultures in normal K+ medium.
- Examined gene expression changes during granule neuron degeneration.
- Employed immunocytochemistry and vital staining (acridine orange) to localize GCD-10.
- Investigated gcd-10 expression in vivo following optic nerve transection.
Main Results:
- Discovered a novel gene, granule cell death-10 (gcd-10), expressed in microglia and upregulated during early granule neuron cell death.
- gcd-10 is homologous to mouse lysosomal-associated multispanning membrane protein (LAPTm5).
- GCD-10 localization shifted from perinuclear to cytoplasmic in cerebellar cultures, coinciding with lysosomal marker ED1.
- gcd-10 is primarily expressed in the brain and spleen and upregulated after nerve injury in the retina.
Conclusions:
- gcd-10 is a novel gene involved in microglial activation.
- The findings suggest gcd-10 plays a role in lysosomal membrane dynamics during microglial activation in both in vitro and in vivo models.
- gcd-10 may be a key player in the brain's response to neuronal injury.