Evaluation and improvement of protein extraction methods for analysis of skin proteome by noninvasive tape stripping.

Analysis of the human skin proteome is key to understand molecular mechanisms maintaining health or leading to diseases of this important organ. For minimal invasive sampling of skin proteomes, the use of self-adhesive tape strips has been successfully applied. However, the methods previously presented were evaluated on different types of skin samples (e.g. healthy, diseased) and used a variety of cell lysis/protein extraction methods, which renders a systematic comparison and thus the identification of the most efficient protocols difficult. Here, we present a study comparing five different approaches for cell lysis and protein extraction from single tape strip biopsies. Extraction using a detergent mix or 1% SDS proved to be most efficient. Further, we replaced protein precipitation by single-pot, solid-phase-enhanced sample preparation (SP3), which strongly enhanced the number of identified proteins. This fully LC-MS compatible methodology provides a fast and reproducible approach for minimal invasive sampling of human skin proteomes. BIOLOGICAL SIGNIFICANCE: Fast and reproducible minimal invasive sampling of human skin proteomes is a major prerequisite for clinical proteomics studies aiming to decipher molecular mechanisms involved in the homeostasis as well as in the development of diseases. By optimization of tape strip sampling, e.g. the introduction of SP3 sample cleanup prior to LC-MS analysis, the presented protocol leads to yet not reported numbers of protein identifications from healthy human skin. Further, due to its efficiency it allows analysis from minimal sample amounts, e.g. from single tape strips, while established protocols relied on pooling of multiple tape strips. This provides the opportunity to perform spatially (lateral) resolved proteome analyses from different depths of the skin by analysis of consecutive strips.