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Published on: March 26, 2016
Aspartoacylase is a regulated nuclear-cytoplasmic enzyme
Jeremy R Hershfield1, Chikkathur N Madhavarao, John R Moffett
1Dept. of Anatomy, Physiology, and Genetics, USUHS, 4301 Jones Bridge Rd, Bethesda, MD 20814, USA.
Summary
Aspartoacylase (ASPA) is found in both the cytoplasm and nucleus, challenging previous assumptions. This nuclear presence suggests novel roles for ASPA beyond its known function in Canavan Disease.
Area of Science:
- Biochemistry
- Cell Biology
- Neuroscience
Background:
- Aspartoacylase (ASPA) is crucial for CNS function, catalyzing N-acetyl-L-aspartate deacetylation.
- Mutations in ASPA cause Canavan Disease, a fatal dysmyelinating disorder.
- ASPA was traditionally considered a cytoplasmic enzyme involved in myelin synthesis.
Purpose of the Study:
- To investigate the subcellular localization of ASPA in the central nervous system (CNS).
- To determine if ASPA has roles beyond its known cytoplasmic function.
- To characterize the enzymatic activity and oligomeric state of nuclear ASPA.
Main Methods:
- Immunohistochemistry on rat brain and kidney tissues, including ASPA-null mutant rats.
- Subcellular fractionation and Western blotting to analyze protein localization and molecular weight.
- Size-exclusion chromatography to assess ASPA's oligomeric state.
- Expression of a GFP-hASPA fusion protein in COS-7 cells to study nuclear import.
Main Results:
- ASPA was detected in both cytoplasmic and nuclear compartments of rat brain, kidney, and cultured oligodendrocytes.
- Specificity was confirmed using ASPA-null Tremor rats.
- Nuclear fractions showed low enzymatic activity, and ASPA exists as an active monomer (38 kD band).
- Engineered GFP-hASPA demonstrated regulated nuclear-cytoplasmic transport, indicating active import.
Conclusions:
- ASPA is a regulated nuclear-cytoplasmic protein, not exclusively cytoplasmic.
- The nuclear localization suggests potential novel functions of ASPA within the nucleus.
- Further research is needed to elucidate the specific roles of nuclear ASPA.
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