Chemotaxis in the context of "Chemoreceptor"

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⭐ Core Definition: Chemotaxis

Chemotaxis (from chemo- + taxis) is the movement of an organism or entity in response to a chemical stimulus. Somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. This is important for bacteria to find food (e.g., glucose) by swimming toward the highest concentration of food molecules, or to flee from poisons (e.g., phenol). In multicellular organisms, chemotaxis is critical to early development (e.g., movement of sperm towards the egg during fertilization) and development (e.g., migration of neurons or lymphocytes) as well as in normal function and health (e.g., migration of leukocytes during injury or infection). In addition, it has been recognized that mechanisms that allow chemotaxis in animals can be subverted during cancer metastasis, and the aberrant change of the overall property of these networks, which control chemotaxis, can lead to carcinogenesis. The aberrant chemotaxis of leukocytes and lymphocytes also contribute to inflammatory diseases such as atherosclerosis, asthma, and arthritis. Sub-cellular components, such as the polarity patch generated by mating yeast, may also display chemotactic behavior.

Positive chemotaxis occurs if the movement is toward a higher concentration of the chemical in question; negative chemotaxis if the movement is in the opposite direction. Chemically prompted kinesis (randomly directed or nondirectional) can be called chemokinesis.

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👉 Chemotaxis in the context of Chemoreceptor

A chemoreceptor, also known as chemosensor, is a specialized sensory receptor which transduces a chemical substance (endogenous or induced) to generate a biological signal. This signal may be in the form of an action potential, if the chemoreceptor is a neuron, or in the form of a neurotransmitter that can activate a nerve fiber if the chemoreceptor is a specialized cell, such as taste receptors, or an internal peripheral chemoreceptor, such as the carotid bodies. In physiology, a chemoreceptor detects changes in the normal environment, such as an increase in blood levels of carbon dioxide (hypercapnia) or a decrease in blood levels of oxygen (hypoxia), and transmits that information to the central nervous system which engages body responses to restore homeostasis.

In bacteria, chemoreceptors are essential in the mediation of chemotaxis.

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Chemotaxis in the context of Dictyostelium

Dictyostelium is a genus of single- and multi-celled eukaryotic, phagotrophic bacterivores. Though they are Protista and in no way fungal, they traditionally are known as "slime molds". They are present in most terrestrial ecosystems as a normal and often abundant component of the soil microflora, and play an important role in the maintenance of balanced bacterial populations in soils.

The genus Dictyostelium is in the order Dictyosteliida, the so-called cellular slime molds or social amoebae. In turn the order is in the infraphylum Mycetozoa. Members of the order are of great theoretical interest in biology because they have aspects of both unicellularity and multicellularity. The individual cells in their independent phase are common on organic detritus or in damp soils and caves. In this phase they are amoebae. Typically, the amoebal cells grow separately and wander independently, feeding mainly on bacteria. However, they interact to form multi-cellular structures following starvation. Groups of up to about 100,000 cells signal each other by releasing chemoattractants such as cyclic AMP (cAMP) or glorin. They then coalesce by chemotaxis to form an aggregate that becomes surrounded by an extracellular matrix. The aggregate forms a fruiting body, with cells differentiating individually into different components of the final structure. In some species, the whole aggregate may move collectively – forming a structure known as a grex or "slug" – before finally forming a fruiting body. Basic processes of development such as differential cell sorting, pattern formation, stimulus-induced gene expression, and cell-type regulation are common to Dictyostelium and metazoans. For further detail see family Dictyostelid.

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Chemotaxis in the context of Transforming growth factor beta

Transforming growth factor beta (TGF-β) is a multifunctional cytokine belonging to the transforming growth factor superfamily that includes three different mammalian isoforms (TGF-β 1 to 3, HGNC symbols TGFB1, TGFB2, TGFB3) and many other signaling proteins. TGFB proteins are produced by all white blood cell lineages.

Activated TGF-β complexes with cell surface TGF-β receptors to form an active serine/threonine kinase complex. After binding their TGF-β protein ligand, TGF-β receptors assemble into heterotetramers composed of two each of the type 1 and type 2 receptor subunits, both of which are serine/threonine kinases. Upon assembly, the type 2 receptor kinase phosphorylates and activates the type 1 receptor kinase to initiate a signaling cascade. This leads to the activation of different downstream substrates and regulatory proteins, inducing transcription of different target genes that function in differentiation, chemotaxis, proliferation, and activation of many immune cells.

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