Proteoform Imaging Mass Spectrometry
Description: We have developed proteoform imaging mass spectrometry (PiMS) for imaging and identification of proteoforms directly from fresh frozen tissues (1). The technique combines a liquid-based ambient mass spectrometry (MS) imaging technique, nanospray desorption electrospray ionization (nano-DESI), with MS data acquisition and processing for individual ions (I2MS). PiMS has been successfully applied to image multiple tissue types including mouse brain tissues, human kidney tissues, and human liver tissues. In particular, using PiMS in the imaging of human kidney proteoforms, we have identified >170 proteoforms spanning in a mass range of 3 kDa to 70 kDa with <±5 ppm mass accuracy. Top-down MS experiment performed during PiMS was able to characterize >20 proteoforms >20 kDa, which enables the localization of posttranslational modifications (PTMs) and coding single nucleotide polymorphisms (cSNPs) of these proteoforms. Furthermore, >100 proteoform-specific images can be directly generated in a single PiMS experiment, which show distinct localizations of the proteoforms to anatomical structures, functional tissue units, and cellular neighborhoods. Further technical advancement in PiMS will allow for improvement in spatial resolution from 80 µm to 10 µm.
Optical (a) autofluorescence (b) images of adjacent human kidney sections containing the cortex, medulla, and vasculature regions; (c) PAS staining of an adjacent section from the same kidney; (d)-(j) PiMS images of individual proteoforms that selectively illuminate different anatomical regions and cellular neighborhoods. (k-m) composite images of various tissue area specific proteins. Scale bar: 1 mm.
TR&D 7 Development Status: On going
1.P. Su, J. P. McGee, K. R. Durbin, M. A. R. Hollas, M. Yang, E. K. Neumann, J. L. Allen, B. S. Drown, F. A. Butun, J. B. Greer, B. P. Early, R. T. Fellers, J. M. Spraggins, J. Laskin, J. M. Camarillo, J. O. Kafader, N. L. Kelleher, Direct Imaging and Identification of Proteoforms up to 70 kDa from Human Tissue. bioRxiv, 2021.2012.2007.471638 (2021).