Project description:The functions of proteins depend on their spatial and temporal distributions, which are not directly measured by static protein abundance. Under endoplasmic reticulum (ER) stress, the unfolded protein response (UPR) pathway remediates proteostasis in part by altering the turnover kinetics and spatial distribution of proteins. A global view of these spatiotemporal changes has yet to emerge and it is unknown how they affect different cellular compartments and pathways. Here we describe a mass spectrometry-based proteomics strategy and data analysis pipeline, termed Simultaneous Proteome Localization and Turnover (SPLAT), to measure concurrently the changes in protein turnover and subcellular distribution in the same experiment. Investigating two common UPR models of thapsigargin and tunicamycin challenge in human AC16 cells, we find that the changes in protein turnover kinetics during UPR varies across subcellular localizations, with overall slowdown but an acceleration in endoplasmic reticulum and Golgi proteins involved in stress response. In parallel, the spatial proteomics component of the experiment revealed an externalization of amino acid transporters and ion channels under UPR, as well as the migration of RNA-binding proteins toward an endosome co-sedimenting compartment. The SPLAT experimental design classifies heavy and light SILAC labeled proteins separately, allowing the observation of differential localization of new and old protein pools and capturing a partition of newly synthesized EGFR and ITGAV to the ER under stress that suggests protein trafficking disruptions. Finally, application of SPLAT toward human induced pluripotent stem cell derived cardiomyocytes (iPSC-CM) exposed to the cancer drug carfilzomib, identified a selective disruption of proteostasis in sarcomeric proteins as a potential mechanism of carfilzomib-mediated cardiotoxicity. Taken together, this study provides a global view into the spatiotemporal dynamics of human cardiac cells and demonstrates a method for inferring the coordinations between spatial and temporal proteome regulations in stress and drug response.
Project description:The functionality of proteins is dependent on their spatial and temporal distributions, neither of which is directly measured by static protein abundance. Here we report a mass spectrometry-based proteomics workflow and data analysis pipeline, named Simultaneous Proteome Localization and Turnover (SPLAT), to concurrently examine the turnover dynamics and subcellular distributions of whole cell proteomes under perturbation. SPLAT builds on prior work in protein turnover measurements and subcellular localization profiling, by combining dynamic stable isotope labeling, differential ultracentrifugation, and kinetic modeling to concurrently measure changes in protein turnover and subcellular localization under perturbation in one experiment.
Project description:Protein degradation plays important roles in biological processes and is tightly regulated. Further, targeted proteolysis is an emerging research tool and therapeutic strategy. However, proteome-wide technologies to investigate the causes and consequences of protein degradation in biological systems are lacking. We developed "multiplexed proteome dynamics profiling" (mPDP), a mass-spectrometry-based approach combining dynamic-SILAC labeling with isobaric mass tagging for multiplexed analysis of protein degradation and synthesis. In three proof-of-concept studies, we uncover different responses induced by the bromodomain inhibitor JQ1 versus a JQ1 proteolysis targeting chimera; we elucidate distinct modes of action of estrogen receptor modulators; and we comprehensively classify HSP90 clients based on their requirement for HSP90 constitutively or during synthesis, demonstrating that constitutive HSP90 clients have lower thermal stability than non-clients, have higher affinity for the chaperone, vary between cell types, and change upon external stimuli. These findings highlight the potential of mPDP to identify dynamically controlled degradation mechanisms in cellular systems.
Project description:MS1 full scan based quantification is one of the most popular approaches for large-scale proteome quantification. Typically only three different samples can be differentially labeled and quantified in a single experiment. Here we present a two stages stable isotope labeling strategy which allows six different protein samples (six-plex) to be reliably labeled and simultaneously quantified at MS1 level. Briefly in the first stage, isotope lysine-d0 (K0) and lysine-d4 (K4) are in vivo incorporated into different protein samples during cell culture. Then in the second stage, three of K0 and K4 labeled protein samples are digested by lysine C and in vitro labeled with light (2CH3), medium (2CD2H), and heavy (2(13)CD3) dimethyl groups, respectively. We demonstrated that this six-plex isotope labeling strategy could successfully investigate the dynamics of protein turnover in a high throughput manner.
Project description:The nucleolus is essential for ribosome biogenesis and is involved in many other cellular functions. We performed a systematic spatiotemporal dissection of the human nucleolar proteome using confocal microscopy. In total, 1,318 nucleolar proteins were identified; 287 were localized to fibrillar components, and 157 were enriched along the nucleoplasmic border, indicating a potential fourth nucleolar subcompartment: the nucleoli rim. We found 65 nucleolar proteins (36 uncharacterized) to relocate to the chromosomal periphery during mitosis. Interestingly, we observed temporal partitioning into two recruitment phenotypes: early (prometaphase) and late (after metaphase), suggesting phase-specific functions. We further show that the expression of MKI67 is critical for this temporal partitioning. We provide the first proteome-wide analysis of intrinsic protein disorder for the human nucleolus and show that nucleolar proteins in general, and mitotic chromosome proteins in particular, have significantly higher intrinsic disorder level compared to cytosolic proteins. In summary, this study provides a comprehensive and essential resource of spatiotemporal expression data for the nucleolar proteome as part of the Human Protein Atlas.
Project description:The functionality of proteins is dependent on their spatial and temporal distributions, neither of which is directly measured by static protein abundance. Here we report a mass spectrometry-based proteomics workflow and data analysis pipeline, named Simultaneous Proteome Localization and Turnover (SPLAT), to concurrently examine the turnover dynamics and subcellular distributions of whole cell proteomes under perturbation. SPLAT builds on prior work in protein turnover measurements and subcellular localization profiling, by combining dynamic stable isotope labeling, differential ultracentrifugation, and kinetic modeling to concurrently measure changes in protein turnover and subcellular localization under perturbation in one experiment.
Briefly, dynamic SILAC labeled cell lysates were fractionated with ultracentrifugation, digested using a modified FASP protocol, and multiplexed with TMT-10 plex tags. The pooled sample was then fractionated with RPLC and injected into an Orbitrap Fusion Tribrid mass spectrometer coupled to an LC with electrospray ionization source operated in data dependent acquisition mode.
Detailed methods can be found in the submission files.
Project description:To examine the protein spatial and temporal changes upon carfilzomib-mediated proteasome inhibition in cardiac cells, we produced human iPSC-derived cardiomyocytes using a standard small molecule based protocol. Cardiomyocyte identity was confirmed by morphology, observation of contraction, and the presence of GFP tagged MLC-2a in the reporter line. We then applied the SPLAT protocol to untreated and carfilzomib-exposed iPSC-cardiomyocytes.
Project description:The functionality of proteins is dependent on their spatial and temporal distributions, neither of which is directly measured by static protein abundance. Here we report a mass spectrometry-based proteomics workflow and data analysis pipeline, named Simultaneous Proteome Localization and Turnover (SPLAT), to concurrently examine the turnover dynamics and subcellular distributions of whole cell proteomes under perturbation. SPLAT builds on prior work in protein turnover measurements and subcellular localization profiling, by combining dynamic stable isotope labeling, differential ultracentrifugation, and kinetic modeling to concurrently measure changes in protein turnover and subcellular localization under perturbation in one experiment.
Briefly, dynamic SILAC labeled cell lysates were fractionated with ultracentrifugation, digested using a modified FASP protocol, and multiplexed with TMT-10 plex tags. The pooled sample was then fractionated with RPLC and injected into Q-Exactive HF orbitrap mass spectrometer coupled to an LC with electrospray ionization source operated in data dependent acquisition mode.
Detailed methods can be found in the submission files.
Project description:Protein homeostasis is an equilibrium of paramount importance that maintains cellular performance by preserving an efficient proteome. This equilibrium avoids the accumulation of potentially toxic proteins, which could lead to cellular stress and death. While the regulators of proteostasis are the machineries controlling protein production, folding and degradation, several other factors can influence this process. Here, we have considered two factors influencing protein turnover: the subcellular localization of a protein and its functional state. For this purpose, we used an imaging approach based on the pulse-labeling of 17 representative SNAP-tag constructs for measuring protein lifetimes. With this approach, we obtained precise measurements of protein turnover rates in several subcellular compartments. We also tested a selection of mutants modulating the function of three extensively studied proteins, the Ca2+ sensor calmodulin, the small GTPase Rab5a and the brain creatine kinase (CKB). Finally, we followed up on the increased lifetime observed for the constitutively active Rab5a (Q79L), and we found that its stabilization correlates with enlarged endosomes and increased interaction with membranes. Overall, our data reveal that both changes in protein localization and functional state are key modulators of protein turnover, and protein lifetime fluctuations can be considered to infer changes in cellular behavior.
Project description:To examine the protein spatial and temporal changes upon carfilzomib-mediated proteasome inhibition in cardiac cells, we produced human iPSC-derived cardiomyocytes using a standard small molecule based protocol. Cardiomyocyte identity was confirmed by morphology, observation of contraction, and the presence of GFP tagged MLC-2a in the reporter line. We then applied the SPLAT protocol to untreated and carfilzomib-exposed iPSC-cardiomyocytes.