Subcellular phosphoproteomics

Abstract

Protein phosphorylation represents one of the most extensively studied post-translational modifications, primarily due to the emergence of sensitive methods enabling the detection of this modification both in vitro and in vivo. The availability of enrichment methods combined with sensitive mass spectrometry instrumentation has played a crucial role in uncovering the dynamic changes and the large expanding repertoire of this reversible modification. The structural changes imparted by the phosphorylation of specific residues afford exquisite mechanisms for the regulation of protein functions by modulating new binding sites on scaffold proteins or by abrogating protein-protein interactions. However, the dynamic interplay of protein phosphorylation is not occurring randomly within the cell but is rather finely orchestrated by specific kinases and phosphatases that are unevenly distributed across subcellular compartments. This spatial separation not only regulates protein phosphorylation but can also control the activity of other enzymes and the transfer of other post-translational modifications. While numerous large-scale phosphoproteomics studies highlighted the extent and diversity of phosphoproteins present in total cell lysates, the further understanding of their regulation and biological activities require a spatio-temporal resolution only achievable through subcellular fractionation. This review presents a first account of the emerging field of subcellular phosphoproteomics where cell fractionation approaches are combined with sensitive mass spectrometry methods to facilitate the identification of low abundance proteins and to unravel the intricate regulation of protein phosphorylation.

The Protein Tyrosine Phosphatase SHP-1 Regulates Phagolysosome Biogenesis

“…Indeed, characterization of the phagosome phosphoproteome and molecular analysis of the evolution of phagosomes highlighted the importance of phosphorylation in the regulation of phagolysosome biogenesis (4,12,22). This process is accomplished through transient, highly regulated interactions between the phagosome and the cytoskeleton, as well as the early, late, and recycling endocytic compartments (46)(47)(48).…”

“…The newly formed phagosome rapidly matures into a phagolysosome where the internalized material is degraded. Phagolysosome biogenesis is a dynamic process, requiring the coordinated action of multiple signaling molecules that regulate the interactions between the phagosome and the cytoskeleton, and the endosomal/lysosomal compartments (2)(3)(4)(5). These interactions are transient and are characterized by the formation of small fusion pores between the two organelles, allowing the exchange of membrane and contents (6).…”

Improving the Selectivity of the Phosphoric Acid β-Elimination on a Biotinylated Phosphopeptide

“…For each species, the area of the peak corresponds to the sum of the whole isotopic pattern. The same treatment was performed on {−H 3 PO 4 …”

“…Introduction P rotein phosphorylation is among the most abundant post-translational modification (PTM) to date [1][2][3] and plays a major role in biological functions [4][5][6][7][8]. Up to a third of human proteins could be phosphorylated at one or several points [9], mostly on serine (≈90 %), threonine (≈10 %), and tyrosine residues (≈1 %) [10].…”

The Role of Mitochondria in Syncytiotrophoblast Cells: Bioenergetics and Steroidogenesis

“…It has been shown that the activity of certain proteins modulated by phosphorylation/ dephosphorylation has a temporary effect in specific cellular regions such as the plasma membrane, endoplasmic reticulum, and nucleus, regulating the cellular metabolism (Trost, 2010;Bauman & Scott, 2002), a system that seems to be associated with steroidogenesis (Gómez-Concha et al, 2011), similar to StAR protein (Steroidogenic acute regulatory protein) in adrenal glands and gonads. StAR protein phosphorylation mediated by PKA stimulates the transport of cholesterol from the cytoplasm into mitochondrial membranes (Stocco, 2000;Thomson, 1998;, apparently through a multiprotein complex associated to this organelle (Thomson, 2002) (Fig.10).…”