| 词条 | Cell–cell recognition |
| 释义 |
FundamentalsCell-cell recognition occurs when two molecules restricted to the plasma membranes of different cells bind to each other. Rather than induce a distal response, like secreted hormones may do, this type of binding brings the cells with the signalling molecules into close proximity with each other. These events can be grouped into two main categories: Intrinsic Recognition and Extrinsic Recognition. Intrinsic Recognition is when cells that are part of the same organism associate. Extrinsic Recognition is when the cell of one organism recognizes a cell from another organism, like when a mammalian cell detects a unicellular microorganism in the body. The molecules that complete this binding can include proteins, carbohydrates, and lipids, resulting in a variety of glycoproteins, lipoproteins, and glycolipoproteins. This recognition is not always protein binding to protein. Proteins binding to glycans occurs in immune response and cell adhesion with leukocytes and platelet cells.[3]. Biological FunctionsCell Recognition in the Immune SystemCells with immune system recognition abilities include macrophages, dentritic cells, T cells, and B cells. The function of innate immunity is a cell-cell recognition between Pattern Recognition Receptors (PRRs) of Phagocytes and Pathogen Associated Molecular Patterns (PAMPs) in Pathogenic Microorganisms. One type of PRR is a group of integral membrane glycoproteins called TLRs, which can recognize certain lipoproteins, peptidoglycan, CpG-rich DNA, and flagellar components in bacterial cells, as well as glycoproteins and phospholipids from protozoan parasites and condidia (fungal spores). These the binding of PAMPs to TLR proteins generally results in an internal signalling cascade including a number of phosphorylations and ubiquitinations that eventually leads to the transcription of genes related to inflammation. The use of TLRs by cells in the innate immune system has lead to an evolutionary battle between pathogenic cells developing different PAMPs that cannot be recognized and immune cells developing new membrane proteins that can recognize them [4]. Cell Recognition for Injury ResponseWhen a large multi-cellular organism sustains an injury, cell-cell recognition is often involved in bringing certain types of cells to the site of an injury. A common example of this is selectin-expressing cells in animals. Selectin in a receptor protein found on the membranes of leukocytes, platelet cells, and endothelial cells that binds membrane-bound glycans. In response to an injury, endothelial cells will express selectin, which binds to glycans present on the leukocyte cell surface. Platelet cells, which are involved in tissue repair, use their selectins to associate with leukocytes on the way to the endothelial cells. Leukocytes then use their own selectins to recognize potential pathogens at the site of the injury. In this manner, the appropriate cells are brought to the site of an injury to deal with immediate repair or invading microorganisms[5]. Growth and DevelopmentOne of the more basic versions cell-cell recognition for adhesion can be observed in Sponges, the most primitive group in the animal kingdom. Sponges develop through the aggregation of individual cells into larger clusters. Through membrane binding proteins and secreted ions, individual sponge cells are able to coordinate aggregation while preventing fusion between difference species or even different individuals. This was discovered when attempts to graft sponge cells from different species or individuals of the same species failed, while attempts using cells from the same individual merged successfully. This is likely due to distinct cadherins, a calcuim-binding membrane protein, expressed by different sponge species and individuals[6]. Cadherins are present in more complex organisms as well. In mouse embryos, E-cadherin on cell membranes is responsible for the adhesion of cells needed for embryonic compaction[7]. Associated Diseases and DisordersExamplesCell–cell recognition is critical to life and can be observed during:
References1. ^1 Campbell, et al., Biology, Eighth Edition, 2008 Pearson Education Inc. 2. ^1 Schnaar, Ronald L., Research Goals, "Link", 1 May 2010 3. ^Ajit Varki and John B Lowe, Biological Roles of Glycans, Essentials of Glycobiology, 2nd Edition Cold Spring Harbor, 2009 4. ^Arika Shizou, Uematsu S, Takeuchi O. "Pathogen Recognition and Innate Immunity" Cell Feb 5 2006 5. ^Richard D Cummings and Rodger P McEver, C-type lectins, Essentials of Glycobiology, 2nd Edition Cold Spring Harbor, 2009 6. ^Xavier Fernandez-Busquets and Max M Burger, Cell Adhesion and Histocompatibility in Sponges. Microscopy Research and Technique. 1999. 44:204-218 7. ^CB Li, LL Hu, ZD Wang, SQ Zhong, L Lei. Regulation of compaction initiation in mouse embryo. Yi Chaun 2009 31(12):1177-1184 External links
1 : Cell communication |
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