Localization of the lens intermediate filament switch by imaging mass spectrometry. (September 2020)

• Record Type: Journal Article
• Authors: Wang, Zhen; Ryan, Daniel J.; Schey, Kevin L.
• Is Part Of: Experimental eye research. Volume 198(2020)
• Publication Date: 2020-09
• Subjects: Imaging mass spectrometry -- Lens fiber cell -- Lens protein -- Vimentin -- Filensin -- CP49 -- Image segmentation; Ophthalmology -- Periodicals; Eye -- Periodicals; Œil -- Périodiques; Ophthalmology; Periodicals; Electronic journals; 612.8405
• DOI: 10.1016/j.exer.2020.108134
• Languages: English
• ISSNs: 0014-4835

Abstract

Abstract: Imaging mass spectrometry (IMS) enables targeted and untargeted visualization of the spatial localization of molecules in tissues with great specificity. The lens is a unique tissue that contains fiber cells corresponding to various stages of differentiation that are packed in a highly spatial order. The application of IMS to lens tissue localizes molecular features that are spatially related to the fiber cell organization. Such spatially resolved molecular information assists our understanding of lens structure and physiology; however, protein IMS studies are typically limited to abundant, soluble, low molecular weight proteins. In this study, a method was developed for imaging low solubility cytoskeletal proteins in the lens; a tissue that is filled with high concentrations of soluble crystallins. Optimized tissue washes combined with on-tissue enzymatic digestion allowed successful imaging of peptides corresponding to known lens cytoskeletal proteins. The resulting peptide signals facilitated segmentation of the bovine lens into molecularly distinct regions. A sharp intermediate filament transition from vimentin to lens-specific beaded filament proteins was detected in the lens cortex. MALDI IMS also revealed the region where posttranslational myristoylation of filensin occurs and the results indicate that truncation and myristoylation of filensin starts soon after filensin expression increased in the inner cortex. From intermediate filament switch to filensin truncation and myristoylation, multiple remarkable changes occur in the narrow region of lens cortex. MALDI images delineated the boundaries of distinct lens regions that will guide further proteomic and interactomic studies. Highlights: New tissue preparation allows imaging mass spectrometry of lens cytoskeletal proteins. Imaging mass spectrometry shows distinct molecular zones across lens. Location of intermediate filament switch in lens cortex revealed in images.