Functional proteomics of cellular mechanosensing mechanisms

Phosphoproteomic Analysis and Protein-Protein Interaction of Rat Aorta GJA1 and Rat Heart FKBP1A after Secoiridoid Consumption from Virgin Olive Oil: A Functional Proteomic Approach

Protein functional interactions could explain the biological response of secoiridoids (SECs), main phenolic compounds in virgin olive oil (VOO). The aim was to assess protein-protein interactions (PPIs) of the aorta gap junction alpha-1 (GJA1) and the heart peptidyl-prolyl cis-trans isomerase (FKBP1A), plus the phosphorylated heart proteome, to describe new molecular pathways in the cardiovascular system in rats using nanoliquid chromatography coupled with mass spectrometry. PPIs modified by SECs and associated with GJA1 in aorta rat tissue were calpain, TUBA1A, and HSPB1. Those associated with FKBP1A in rat heart tissue included SUCLG1, HSPE1, and TNNI3. In the heart, SECs modulated the phosphoproteome through the main canonical pathways PI3K/mTOR signaling (AKT1S1 and GAB2) and gap junction signaling (GAB2 and GJA1). PPIs associated with GJA1 and with FKBP1A, the phosphorylation of GAB2, and the dephosphorylation of GJA1 and AKT1S1 in rat tissues are promising protein targets promoting cardiovascular protection to explain the health benefits of VOO.

Nuclear decoupling is part of a rapid protein-level cellular response to high-intensity mechanical loading

Studies of cellular mechano-signaling have often utilized static models that do not fully replicate the dynamics of living tissues. Here, we examine the time-dependent response of primary human mesenchymal stem cells (hMSCs) to cyclic tensile strain (CTS). At low-intensity strain (1 h, 4% CTS at 1 Hz), cell characteristics mimic responses to increased substrate stiffness. As the strain regime is intensified (frequency increased to 5 Hz), we characterize rapid establishment of a broad, structured and reversible protein-level response, even as transcription is apparently downregulated. Protein abundance is quantified coincident with changes to protein conformation and post-translational modification (PTM). Furthermore, we characterize changes to the linker of nucleoskeleton and cytoskeleton (LINC) complex that bridges the nuclear envelope, and specifically to levels and PTMs of Sad1/UNC-84 (SUN) domain-containing protein 2 (SUN2). The result of this regulation is to decouple mechano-transmission between the cytoskeleton and the nucleus, thus conferring protection to chromatin.

Understanding the Extracellular Matrix to Enhance Stem Cell-Based Tissue Regeneration

The extracellular matrix is a biologically critical entity that has historically been poorly understood. Here we discuss how new tools for characterizing matrix composition and function enable us to design and deliver advanced matrices in vitro, to optimize regeneration, and in vivo, within a variety of tissues and organs.

Proteomic profile of TGF-β1 treated lung fibroblasts identifies novel markers of activated fibroblasts in the silica exposed rat lung

We performed liquid chromatography-tandem mass spectrometry (LC-MS/MS) on control and TGF-β1-exposed rat lung fibroblasts to identify proteins differentially expressed between cell populations. A total of 196 proteins were found to be differentially expressed in response to TGF-β1 treatment. Guided by these results, we next determined whether similar changes in protein expression were detectable in the rat lung after chronic exposure to silica dust. Of the five proteins selected for further analysis, we found that levels of all proteins were markedly increased in the silica-exposed rat lung, including the proteins for the very low density lipoprotein receptor (VLDLR) and the transmembrane (type I) heparin sulfate proteoglycan called syndecan 2 (SDC2). Because VLDLR and SDC2 have not, to our knowledge, been previously linked to the pathobiology of silicosis, we next examined whether knockdown of either gene altered responses to TGF-β1 in MRC-5 lung fibroblasts. Interestingly, we found knockdown of either VLDLR or SDC2 dramatically reduced collagen production to TGF-β1, suggesting that both proteins might play a novel role in myofibroblast biology and pathogenesis of silica-induced pulmonary fibrosis. In summary, our findings suggest that performing LC-MS/MS on TGF-β1 stimulated lung fibroblasts can uncover novel molecular targets of activated myofibroblasts in silica-exposed lung.