Oleg
Broytman
E-mail: obroytman@wisc.edu
Research Project:
Amyloid Precursor Protein (APP) is a 695771 amino acid transmembrane protein highly expressed in the central nervous system. From its membrane spanning domain, beta-amyloid is cleaved. The deposition of beta-amyloid is likely pivotal to neuronal loss and onset of dementia in Alzheimer’s Disease (AD). Cellular APP levels and downstream beta-amyloid production are closely correlated with the abundance of the APP mRNA in both Down’s Syndrome, where each cell carries an extra copy of the APP gene, and in late onset AD patients, as compared to age-matched controls. It is, therefore, important to elucidate the mechanisms through which the levels of APP mRNA are regulated, as this could provide a therapeutic target for reducing production of beta-amyloid.
APP mRNA contains two 3’UTR regulatory elements. One of these
elements, a 29-base sequence two hundred bases downstream of the
stop codon, acts as a destabilizer. When nucleolin or hnRNP C,
two mRNA-binding proteins, bind to this element, they ablate its
function and increase the longevity of APP mRNA by 2 3 fold.
The other regulatory element, recently discovered by the Malter
lab, spans 50 bases immediately 3’ to the stop codon. This
element (50-sce) acts as a stabilizer when it is deleted,
mutant mRNA is degraded 4 fold faster in both in-vitro mRNA decay
systems and intact cells (unpublished data). Electrophoretic mobility
shift assays show that at least one cytoplasmic protein, and possibly
several, bind specifically to the 50sce. The identity of this protein
is not known, and clear evidence that it is the binding of this
protein complex to 50sce that regulates APP mRNA stability is not
available (although we do have circumstantial evidence). My research
is aimed at purifying and characterizing the 50-sce binding protein
and proving that it regulates the rate of APP mRNA decay.
Abstracts and Publications:
- Broytman, O., P.R. Westmark, Z. Gurel, and J.S. Malter. 2008. Rck/p54 interacts with APP mRNA as part of a multi-protein complex and enhances APP mRNA and protein expression in neuronal cell lines. Neurobiol. Aging. [PDF]
- Broytman, O. and J.S. Malter. 2004. Anti-Albeta: The good, the bad and the unforseen. J. Neurosci. Res. 75: 301-306.