\subsection*{Alzheimer's Disease - Analysis of modified proteins in an UBB$^+$$^1$ transgenic mouse with endogenous proteasome inhibition}

\textbf{Schulenborg T}$^1$, van Leeuwen FW$^2$, Meyer HE$^1$, Marcus K$^1$\\
\begin{spacing}{1}
\noindent $^1$Medizinisches Proteom-Center, Ruhr-Universität Bochum, Bochum, Germany\\
$^2$Netherlands Institute for Neuroscience, Meibergdreef 47, 1105BA Amsterdam, The Netherlands\\
\end{spacing}

\noindent Ubiquitin-B$^+$$^1$ (UBB$^+$$^1$) - a mutant form of ubiquitin lacking glycine-76 - was found to accumulate in the neuropathological hallmarks of Alzheimer's Disease (AD) and aggregates of other neurodegenerative diseases. UBB+1 is crucial for ubiquitination of aberrant proteins and is ubiquitinated itself on Lys29 and Lys48. In neurodegenerative disorders it additionally presents an ubiquitin fusion degradation substrate blocking proteasomal degradation. A reduction of proteasomal activity allows the accumulation of ubiquitinated UBB$^+$$^1$ (UBB$^+$$^1$-ub) and other ubiquitinated proteins, higher levels of UBB$^+$$^1$-ub promotes proteasome inhibiton and contributes to aggregate formation and cell death. In order to asses the function of UBB$^+$$^1$ and its downstream effects a transgenic mouse line was established expressing UBB$^+$$^1$ protein in the brain. 
In our project we analyse effects of high UBB$^+$$^1$ expression levels on the proteome in the cortices of these mice. We are especially interested in changes of protein modification such as phosphorylation because protein phosphorylation is known to play an important role in AD (e.g. hyperphosphorylated tau and presenilin). Additionally oxidised proteins are in the focus of our analyses as one of the prevalent effects in AD is the increase of oxidative stress resulting in higher levels of oxidised protein species. 
Sophisticated proteomic technologies like 2D-DIGE combined with staining procedures specific for phosphorylated and oxidised proteins are used for differential proteome analysis. Protein identification and the localisation of modified amino acids is performed by mass spectrometry. So far several phosphorylated proteins were identified to be regulated in the cortices of the UBB+1 mice. The validation of these results by immunoblotting is still under work.

\clearpage