Streamlined Biotinylation, Enrichment and Analysis for Enhanced Plasma Membrane Protein Identification Using TurboID and TurboID-Start Biotin Ligases

Plasma membrane proteins (PMPs) play pivotal roles in various cellular events and are crucial in disease pathogenesis, making their comprehensive characterization vital for biomedical research. However, the hydrophobic nature and low expression levels of PMPs pose challenges for conventional enrichment methods, hindering their identification and functional profiling. In this study, we presented a novel TurboID-based enrichment approach for PMPs that helped overcoming some of the existing limitations. We evaluated the efficacy of TurboID and its modified form, TurboID-START, in PMP enrichment, achieving efficient and targeted labelling of PMPs without the need for stable cell line generation. This approach resulted reduction in non-specific biotinylation events, leading to improved PMP enrichment and enabled assessment of the subcellular proteome associated with the plasma membrane. Our findings paved the way for studies targeting the dynamic nature of the plasma membrane proteome and aiming to capture transient associations of proteins with the plasma membrane. The novel TurboID-based enrichment approach presented here offers promising prospects for in-depth investigations into PMPs and their roles in cellular processes.

Gel-based and gel-free search for plasma membrane proteins in chickpea (Cicer arietinum L.) augments the comprehensive data sets of membrane protein repertoire

Plasma membrane (PM) encompasses total cellular contents, serving as semi-porous barrier to cell exterior. This living barrier regulates all cellular exchanges in a spatio-temporal fashion. Most of the essential tasks of PMs including molecular transport, cell-cell interaction and signal transduction are carried out by their proteinaceous components, which make the PM protein repertoire to be diverse and dynamic. Here, we report the systematic analysis of PM proteome of a food legume, chickpea and develop a PM proteome reference map. Proteins were extracted from highly enriched PM fraction of four-week-old seedlings using aqueous two-phase partitioning. To address a population of PM proteins that is as comprehensive as possible, both gel-based and gel-free approaches were employed, which led to the identification of a set of 2732 non-redundant proteins. These included both integral proteins having bilayer spanning domains as well as peripheral proteins associated with PMs through posttranslational modifications or protein-protein interactions. Further, the proteins were subjected to various in-silico analyses and functionally classified based on their gene ontology. Finally an inventory of the complete set of PM proteins, identified in several monocot and dicot species, was created for comparative study with the generated PM protein dataset of chickpea.

BIOLOGICAL SIGNIFICANCE

Chickpea, a rich source of dietary proteins, is the second most cultivated legume, which is grown over 10 million hectares of land worldwide. The annual global production of chickpea hovers around 8.5 million metric tons. Recent chickpea genome sequencing effort has provided a broad genetic basis for highlighting the important traits that may fortify other crop legumes. Improvement in chickpea varieties can further strengthen the world food security, which includes food availability, access and utilization. It is known that the phenotypic trait of a cultivar is the manifestation of the orchestrated functions of its proteins. Study of the PM proteome offers insights into the mechanism of communication between the cell and its environment by identification of receptors, signalling proteins and membrane transporters. Knowledge of the PM protein repertoire of a relatively dehydration tolerant chickpea variety, JG-62, can contribute in development of strategies for metabolic reprograming of crop species and breeding applications.

Bovine sperm plasma membrane proteomics through biotinylation and subcellular enrichment

A significant proportion of mammalian fertilization is mediated through the proteomic composition of the sperm surface. These protein constituents can present as biomarkers to control and regulate breeding of agricultural animals. Previous studies have addressed the bovine sperm cell apical plasma membrane (PM) proteome with nitrogen cavitation enrichment. Alternative workflows would enable to expand the compositional data more globally around the entire sperm's surface. We used a cell surface biotin-labeling in combination with differential centrifugation to enrich sperm surface proteins. Using nano-LC MS/MS, 338 proteins were confidently identified in the PM-enriched proteome. Functional categories of sperm-egg interaction, protein turnover, metabolism as well as molecular transport, spermatogenesis, and signal transduction were represented by proteins with high quantitative signal in our study. A highly significant degree of enrichment was found for transmembrane and PM-targeted proteins. Among them, we also report proteins previously not described on bovine sperm (CPQ, CD58, CKLF, CPVL, GLB1L3, and LPCAT2B) of which CPQ and CPVL cell surface localization was further validated. A descriptive overview of the bovine sperm PM integral and peripheral proteins is provided to complement future studies on animal reproduction and its relation to sperm cell surface. All MS data have been deposited in the ProteomeXchange with identifier PXD001096 (http://proteomecentral.proteomexchange.org/dataset/PXD001096).

The plasma membrane proteome of maize roots grown under low and high iron conditions

Iron (Fe) homeostasis is essential for life and has been intensively investigated for dicots, while our knowledge for species in the Poaceae is fragmentary. This study presents the first proteome analysis (LC-MS/MS) of plasma membranes isolated from roots of 18-day old maize (Zea mays L.). Plants were grown under low and high Fe conditions in hydroponic culture. In total, 227 proteins were identified in control plants, whereas 204 proteins were identified in Fe deficient plants and 251 proteins in plants grown under high Fe conditions. Proteins were sorted by functional classes, and most of the identified proteins were classified as signaling proteins. A significant number of PM-bound redox proteins could be identified including quinone reductases, heme and copper-containing proteins. Most of these components were constitutive, and others could hint at an involvement of redox signaling and redox homeostasis by change in abundance. Energy metabolism and translation seem to be crucial in Fe homeostasis. The response to Fe deficiency includes proteins involved in development, whereas membrane remodeling and assembly and/or repair of Fe-S clusters is discussed for Fe toxicity. The general stress response appears to involve proteins related to oxidative stress, growth regulation, an increased rigidity and synthesis of cell walls and adaption of nutrient uptake and/or translocation. This article is part of a Special Issue entitled: Plant Proteomics in Europe.

Two-dimensional liquid chromatography analysis of differential proteome of liver plasma membrane in mice with endotoxic shock

AIM: To establish and optimize the methods for plasma membrane proteome research, and comparatively analyze plasma membrane proteomes of normal control group and the group treated with LPS for 3 h.

METHODS: Twenty BALB/c mice were assigned to 2 groups: the control group and LPS-treated group. Plasma membrane of liver cells from mice was extracted using differential centrifugation and sucrose density-gradient centrifugation. Plasma membrane proteins of two groups were fractionated according to pI using chromatofocusing with analytical columns in the first dimension, followed by separation of the proteins in each pI fraction using nonporous reversed-phase high performance liquid chromatography (HPLC). A two-dimensional map of the protein content for each group based upon pI versus hydrophobicity as detected by UV absorption was generated and a differential display map indicating the presence of up- or down-regulated proteins was exhibited using ProteoVue and DeltaVue software.

RESULTS: Image analysis of two-dimensional map revealed 24 differentially expressed proteins between the normal control group and that treated with LPS for 3 h. Compared with normal control, 16 protein fractions were up-regulated and 8 protein fractions were down-regulated in the group treated with LPS for 3 h.

CONCLUSION: There is a significant difference of plasma membrane proteome between the normal control and the mice treated with LPS.