Systematic Identification of Single Amino Acid Variants in Glioma Stem-Cell-Derived Chromosome 19 Proteins

Novel
proteoforms with single amino acid variations represent proteins
that often have altered biological functions but are less explored
in the human proteome. We have developed an approach, searching high
quality shotgun proteomic data against an extended protein database,
to identify expressed mutant proteoforms in glioma stem cell (GSC)
lines. The systematic search of MS/MS spectra using PEAKS 7.0 as the
search engine has recognized 17 chromosome 19 proteins in GSCs with
altered amino acid sequences. The results were further verified by
manual spectral examination, validating 19 proteoforms. One of the
novel findings, a mutant form of branched-chain aminotransferase 2
(p.Thr186Arg), was verified at the transcript level
and by targeted proteomics in several glioma stem cell lines. The
structure of this proteoform was examined by molecular modeling in
order to estimate conformational changes due to mutation that might
lead to functional modifications potentially linked to glioma. Based
on our initial findings, we believe that our approach presented could
contribute to construct a more complete map of the human functional
proteome.