Cell Type–specific labeling using Amino acid Precursors (CTAP) is an approach for introducing stable-isotope labeled amino acids into the proteome of distinct cell types in multicellular culture. In short, transgenic expression of exogenous amino acid biosynthesis enzymes allows vertebrate cells to overcome their dependence on supplemented essential amino acids through supplementation of precursors to these amino acids. These transgenic cells can be selectively labeled through metabolic incorporation of amino acids produced from heavy isotope–labeled precursors. In coculture, expression of distinct amino acid biosynthesis enzymes in each cell type enables continuous cell-selective proteome labeling using differentially labeled precursors. Quantitative mass spectrometry–based analysis of coculture samples can then be used to determine relative abundance of proteins from each cell type.

The CTAP methodology was validated with the essential amino acid l-lysine and a manuscript describing the method can be downloaded directly from the publishers website:

For inquiries please email Nicholas Gauthier, Chris Sander, and Martin Miller: gro/ccksm/oibc//patc

This page contains the CTAP.ms Google Groups Forum. For a direct link to the google groups page, click here

This page contains links to raw LC-MS/MS data for Gauthier et al (2013). For MaxQuant processed versions of these same data, which include the identified peptides/proteins as well as intensity and H/L ratios for each figure, please see the Supplementary Data File on the publishers website here. Other raw data for the manuscript is available through the following:

• Schematics of the vector inserts used in this study can be found in the Supplementary Information File here.
• Oligonucleotide sequences for the vector inserts can also be found in GenBank (modified lyr, DDC, CBZcleaver, and wild-type-lyr).
• Illumina mRNA microarray data can be found in Gene Expression Omnibus (GEO) under accession numbers GSE43894 and GSE43895.

The table below contains RAW LC-MS/MS files for all data presented in the manuscript.