Shotgun proteomic analysis of microdissected postmortem human pituitary using complementary two-dimensional liquid chromatography coupled with tandem mass spectrometer

The pituitary is responsible for multiple homeostatic functions including metabolism, growth and reproduction. Proteome analysis offers an efficient approach for a comprehensive analysis of pituitary protein expression. The pituitary is usually acquired from postmortem specimens, which may potentially affect the proteome profile by proteolysis. The aim of this study was to determine whether the postmortem pituitary could be used in proteomic analysis combining with Laser capture microdissection (LCM). Digested peptides from LCM captured prolactin (PRL) cells were separated by two dimensional-nanoscale liquid chromatography (2D-nanoLC/MS) and characterized by tandem mass spectrometry (MS). All MS/MS spectrums were searched by SEQUEST and a proteome of 1660 proteins was identified. Category analysis of the proteome revealed an extensive unbiased access to cell component proteins with diverse functional characteristics. The results demonstrated the ability of using 2D-nanoLC/MS to perform sensitive proteomic analysis on limited protein quantities through microdissection. Detailed comparisons between the proteome in question and the one derived from the prolactinoma controls at peptide and protein levels indicated that the two proteomes had similar characters. Overall, our results revealed for the first time the possibility of use of postmortem human pituitary for proteomic research which is important for further studies on disease biomarker identification and molecular mechanisms of prolactinoma tumorigenesis.