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Technical Briefs |
2-Macroglobulin
1
Clinical Pathology Department, Warren G. Magnuson Clinical Center
2
Geriatric Psychiatry Branch, National Institute of Mental Health, NIH, Bethesda, MD 20892
a address correspondence to this author at: Clinical Pathology Department, NIH, Bldg. 10, Rm. 2C-407, Bethesda, MD 20892-1508
2-Macroglobulin
(
2M) biochemically is a glycoprotein,
structurally is a tetramer of identical subunits (182 000 Da each),
and functionally is a major human plasma pan-proteinase inhibitor
(1). Its gene (A2M) has been mapped to chromosome
12p12-13 (2). Investigations into the pathogenesis of
Alzheimer disease (AD) revealed that
2M is
associated with senile plaques (3), binds to Aß peptide,
the major component of ß-amyloid (4); attenuates
fibrillogenesis and neurotoxicity of Aß
(4)(5); and mediates Aß degradation
(6)(7). Activated
2M,
apolipoprotein E-enriched lipoproteins, and amyloid precursor protein
share the same neuronal cell surface receptor, LDL
receptor-related protein (
2M-r/LRP)
(3)(7). Consequently, there has been a growing
interest in exploring possible associations between alterations of the
A2M gene and AD risk. Two A2M polymorphisms, both
involving functional domains, have been suggested to be related to AD
risk (8)(9)(10)(11). One involves a pentanucleotide deletion
adjacent to a consensus splice site in intron 17 (5' to exon 18) of
A2M, and it may cause exon skipping (12). The
other involves an A-to-G transition in exon 24, at position 1000 based
on the cDNA sequence (13)(14) or at position 976
based on the mature protein (9), and it changes Ile
(ATC) to Val (GTC) near the thiol ester site of
2M (9). The resulting polymorphism
is of high frequency, with an allele distribution of 6570% A and
3035% G in Caucasian populations (13)(14)(15).
Current evidence for an A2M gene-AD risk connection is,
however, conflicting. Several studies have failed to establish an
association between AD and the
Footnotes
References
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