MALDI-TOF mass spectrometric protein profiling of microvesicles produced by the NK-92 natural killer cell line

Abstract

Extracellular vesicles that are shed from the plasma membrane contain a wide range of molecules, among which are proteins, lipids, nucleic acids, and sugars. The cytotoxic proteins of natural killer cells play a key role in the implementation of their cytolytic functions. One of the important steps in understanding the distant communication of cells is the determination of the proteome of microvesicles. This study was aimed at the protein profiling of the microvesicles produced by the NK-92 natural killer cell line. 986 proteins with a variety of functions were identified in the lysate of microvesicles using the MALDI-TOF mass spectrometric analysis. With automated methods of functional analysis applied, it has been shown that the largest protein groups are hypothetical proteins, proteins with unknown functions, and domains. The most representative groups are also comprised by transcription regulators; intracellular signaling proteins; RNA translation, transcription, processing, and utilization regulators; receptors; protein processing and proteolysis regulators; amino acid metabolism enzymes, as well as transport proteins and transport regulators. Minor functional groups are represented by vitamins and mineral metabolism enzymes, membrane and microdomain-forming proteins, hormones, hemostatic regulators, regulators of sensory systems, specific mitochondrial and Golgi apparatus proteins, and extracellular signaling proteins. An intermediate position is occupied by various functional groups, including cytoskeleton and motor proteins; proteins of centrioles; ion channels and their regulators; proteins of the ubiquitin-proteasome pathway of protein degradation; lipid, steroid, and fatty acid metabolism enzymes; nucleic acid base and carbohydrate metabolism enzymes, as well as energy metabolism enzymes and other proteins involved in intermediate metabolism; proteins of the immune response and inflammation; antigens and histocompatibility proteins; cytokines and growth factors; regulators of apoptosis, autophagy, endocytosis, and exocytosis; regulators of the cell cycle and division; regulators of proliferation, cell differentiation, and morphogenesis; regulators of cell adhesion and matrix metabolism; nuclear transport proteins; transposition proteins; DNA replication and repair proteins, as well as inactive proteins. The data obtained expand the existing knowledge of the distant communication of cells and indicate new mechanisms of interaction between natural killer and target cells.

Keywords

• natural killer cells
• microvesicles
• immune response
• inflammation
• proteome
• maldi-tof mass spectrometry