Proteomics
Proteomics is the large-scale, systematic study of the complete set of proteins — collectively called the proteome — expressed by a cell, tissue, organ or organism at a given point in time. Proteins are the primary functional molecules of living cells — carrying out virtually every biological process including enzyme catalysis, signal transduction, structural support, immune defence, gene regulation and molecular transport. While the genome (the complete set of genes) is essentially fixed and identical in every cell of an organism, the proteome is extraordinarily dynamic — varying between cell types, between physiological states and in response to disease, environmental stress and drug treatment. Proteomics harnesses this dynamism — measuring the identity, abundance, modifications and interactions of thousands of proteins simultaneously — to understand how biological systems function in health and disease.
Overview
The relationship between the genome and the proteome is complex and non-linear. A single gene can give rise to multiple different proteins — through alternative splicing of messenger RNA, post-translational modifications (such as phosphorylation, glycosylation and ubiquitination) and proteolytic cleavage — meaning that the human proteome is far more complex than the approximately 20,000 protein-coding genes in the human genome would suggest. It is estimated that the human proteome contains more than 1 million distinct protein forms — each with potentially different biological activity and disease relevance.
This complexity — combined with the dynamic, context-dependent nature of protein expression — makes proteomics both extraordinarily informative and technically challenging. Modern proteomics technologies — particularly mass spectrometry-based approaches — have dramatically expanded the scope and depth of protein measurement — enabling the simultaneous identification and quantification of thousands to tens of thousands of proteins in a single experiment.
Technologies
Mass Spectrometry-Based Proteomics
Mass spectrometry (MS) is the dominant technology in modern proteomics — enabling high-throughput, sensitive and quantitative measurement of proteins and their modifications. The standard mass spectrometry-based proteomics workflow involves:
- Protein extraction — Extracting proteins from the biological sample
- Enzymatic digestion — Digesting proteins into peptides using proteases such as trypsin
- Liquid chromatography (LC) — Separating peptides by their physicochemical properties before mass spectrometry analysis
- Mass spectrometry — Measuring the mass-to-charge ratio of peptide ions — enabling their identification and quantification
- Database searching — Matching experimental mass spectra to theoretical spectra from protein databases — enabling protein identification
Key mass spectrometry-based proteomics approaches include:
- Discovery proteomics (shotgun proteomics) — Untargeted identification and quantification of all proteins in a sample
- Targeted proteomics (MRM/PRM) — Quantification of specific proteins of interest with high sensitivity and reproducibility
- Phosphoproteomics — Specific enrichment and measurement of phosphorylated proteins — providing a global view of cellular signalling
- Glycoproteomics — Characterisation of glycosylated proteins
Quantitative Proteomics
Several approaches enable quantitative comparison of protein abundance between samples:
- Label-free quantification (LFQ) — Comparing protein abundance between samples based on MS signal intensity — without chemical labelling
- SILAC (Stable Isotope Labelling with Amino acids in Cell culture) — Metabolic labelling of proteins with heavy isotopes — enabling accurate quantitative comparison
- TMT (Tandem Mass Tag) and iTRAQ — Chemical labelling approaches enabling multiplexed quantitative comparison of up to 18 samples simultaneously
Protein Arrays
Protein microarrays — using antibodies or other affinity reagents to capture specific proteins — provide an alternative, high-throughput approach to protein measurement — particularly for targeted measurement of specific protein panels in large numbers of samples.
Applications of Proteomics
Cancer Research
Proteomics has made major contributions to cancer research — enabling comprehensive characterisation of the cancer proteome — identifying cancer-specific protein expression patterns, discovering new drug targets and revealing the molecular mechanisms of cancer drug resistance. The Clinical Proteomic Tumour Analysis Consortium (CPTAC) — a major US National Cancer Institute initiative — has generated comprehensive proteomic and phosphoproteomic maps of multiple cancer types — providing an extraordinary resource for cancer biology research.
Sickle Cell Disease and Thalassaemia
Proteomics has been applied to characterise the proteomic changes in sickle cell disease — revealing alterations in red blood cell proteins, plasma proteins, endothelial proteins and organ-specific proteins driven by haemolysis, oxidative stress and vascular injury. Research conducted by Dr. Nishant Kumar Rana at the University of Colorado Anschutz Medical Campus used proteomics as part of a comprehensive multi-omics profiling approach — alongside RNA-seq and metabolomics — to characterise proteomic alterations in the spleen and liver of SCD and β-thalassaemia mice — generating important insights into the systemic organ-level consequences of haemolytic anaemia and informing the development of new therapeutic strategies for these blood disorders.
Biomarker Discovery
Proteomics is a powerful tool for discovering disease biomarkers — proteins whose abundance in blood, urine or other biofluids reflects the presence, severity or progression of disease. Plasma proteomics — measuring thousands of proteins in blood — is an active area of biomarker discovery for cancer, cardiovascular disease, neurodegeneration and many other conditions.
Drug Target Discovery and Pharmacoproteomics
Proteomics enables the comprehensive characterisation of how drugs alter the proteome — identifying on-target and off-target effects, mechanisms of drug resistance and new therapeutic vulnerabilities. Chemical proteomics — using drug-conjugated beads or activity-based probes — enables direct identification of drug-binding proteins in complex biological samples.
Post-Translational Modification (PTM) Analysis
Post-translational modifications — including phosphorylation, ubiquitination, acetylation, methylation and glycosylation — are critical regulators of protein function. Proteomics technologies — particularly phosphoproteomics — enable global mapping of these modifications — providing a comprehensive view of cellular signalling and regulation.
Multi-Omics Integration
Proteomics is most powerful when integrated with other omics technologies — genomics, transcriptomics (RNA-seq) and metabolomics — in a multi-omics approach that provides a systems-level view of biological processes. The integration of proteomics with RNA-seq and metabolomics — as employed by Dr. Nishant Kumar Rana at the University of Colorado Anschutz Medical Campus in his research on SCD and β-thalassaemia — enables a comprehensive molecular characterisation of disease that captures changes at every level of biological organisation — from gene expression to protein function to metabolic activity.
Proteomics in India
India has a growing proteomics research community — with laboratories at IITs, ICMR-funded institutes, CSIR laboratories and leading universities applying proteomics to understand diseases of particular importance in India — including cancer, tuberculosis, cardiovascular disease, haemoglobinopathies and neurological disorders. Indian researchers — supported by ICMR and UGC fellowships — are contributing to global proteomics research both within India and at leading international institutions.