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The human choline acetyltransferase gene encodes two proteins
D D Grosman1, M V Lorenzi, A C Trinidad
1Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, FL 33101, USA.
Journal of Neurochemistry
|August 1, 1995
Summary
Researchers identified a 27-kDa protein in human brain cells that interacts with choline acetyltransferase (ChAT) but lacks its enzymatic activity. This finding sheds light on the complex regulation of acetylcholine synthesis.
Area of Science:
- Neuroscience
- Molecular Biology
- Genetics
Background:
- Choline acetyltransferase (ChAT) is crucial for synthesizing acetylcholine, a key neurotransmitter.
- Alternative splicing of the human ChAT gene produces 2,500- and 6,000-nucleotide (nt) mRNAs.
Purpose of the Study:
- To investigate the functional and molecular characteristics of proteins encoded by different ChAT mRNA variants.
- To determine if the 6,000-nt ChAT transcript encodes a protein with ChAT activity.
Main Methods:
- In vitro translation of cRNA from the 2,500-nt ChAT mRNA.
- Immunoblotting using antibodies against a predicted 6,000-nt ChAT transcript sequence and the 68-kDa ChAT enzyme.
- Gel-filtration chromatography and immunohistochemistry on human nucleus basalis proteins and spinal cord tissues.
Main Results:
- In vitro translation of the 2,500-nt mRNA yielded a protein with ChAT activity, confirming it encodes the enzyme.
- A 27-kDa protein was detected, cross-reacting with ChAT antibodies but lacking enzymatic activity.
- The 27-kDa protein colocalized with the 68-kDa ChAT enzyme in cholinergic neurons.
Conclusions:
- The 2,500-nt mRNA encodes the active 68-kDa human ChAT enzyme.
- The 6,000-nt ChAT transcript may encode a regulatory or non-enzymatic protein that interacts with ChAT.
- These findings reveal novel aspects of ChAT regulation and function in the human nervous system.