Open AccessSelected reaction monitoring as an effective method for reliable quantification of disease‐associated proteins in maple syrup urine disease
Author(s) -
FernándezGuerra Paula,
Birkler Rune I. D.,
Merinero Begoña,
Ugarte Magdalena,
Gregersen Niels,
RodríguezPombo Pilar,
Bross Peter,
Palmfeldt Johan
Publication year - 2014
Publication title -
molecular genetics and genomic medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.765
H-Index - 29
ISSN - 2324-9269
DOI - 10.1002/mgg3.88
Subject(s) - maple syrup urine disease , gene , amino acid , biology , mitochondrial disease , biochemistry , chemistry , mitochondrial dna , microbiology and biotechnology , leucine
Selected reaction monitoring (SRM) mass spectrometry can quantitatively measure proteins by specific targeting of peptide sequences, and allows the determination of multiple proteins in one single analysis. Here, we show the feasibility of simultaneous measurements of multiple proteins in mitochondria‐enriched samples from cultured fibroblasts from healthy individuals and patients with mutations in branched‐chain α ‐ketoacid dehydrogenase (BCKDH) complex. BCKDH is a mitochondrial multienzyme complex and its defective activity causes maple syrup urine disease (MSUD), a rare but severe inherited metabolic disorder. Four different genes encode the catalytic subunits of BCKDH: E1 α ( BCKDHA ), E1 β ( BCKDHB ), E2 ( DBT ), and E3 ( DLD ). All four proteins were successfully quantified in healthy individuals. However, the E1 α and E1 β proteins were not detected in patients carrying mutations in one of those genes, whereas mRNA levels were almost unaltered, indicating instability of E1 α and E1 β monomers. Using SRM we elucidated the protein effects of mutations generating premature termination codons or misfolded proteins. SRM is a complement to transcript level measurements and a valuable tool to shed light on molecular mechanisms and on effects of pharmacological therapies at protein level. SRM is particularly effective for inherited disorders caused by multiple proteins such as defects in multienzyme complexes.