This gene encodes a protein that belongs to themicrotubule-associated protein family. The proteins of this family were originally isolated since they copurify withtubulin in polymerization experiments: tubulin in cell extracts can be made to polymerize to producemicrotubules (MT) under the influence of heat and the addition ofGTP, and the MT can then be collected by centrifugation. When this is done a series of microtubule associated proteins are collected along with the MT and can be detected bySDS-PAGE and other methods. Brain extracts are rich in several of these proteins, MAP2 being one of these. The single MAP2 gene produces four major transcripts producing four proteins, MAP2A, MAP2B, MAP2C and MAP2D. MAP2A and MAP2B are very high molecular weight proteins, with apparent molecular weight on SDS-PAGE about 250 kDa, while MAP2C and MAP2D are much lower molecular weight forms with apparent SDS-PAGE size about 70 kDa.[7] All forms of MAP2 share a common core sequence which includes MT binding domains, 18 amino acid sequences which are found in other MT associated proteins such asMAP Tau andMAP1B. The MAP2 isoforms are thought to be involved in MT assembly, which is an essential step inneuritogenesis. MAP2 serves to stabilize MT growth by crosslinking MT withintermediate filaments and other MTs. MAP2 isoforms are neuron-specificcytoskeletal proteins enriched indendrites andperikarya, implicating a role in determining and stabilizing neuronal morphology duringneuron development. As a resultantibodies to MAP2 are widely used to identify neuronal cells and trace dendritic processes in experimental contexts.
Neurons were grown in tissue culture and stained with antibody toMAP2 protein in green and antibody to another microtubule associated proteinMAP-tau in red using theimmunofluorescence technique. MAP2 is found only in dendrites and perikarya, while MAP-tau is found not only in the dendrites and perikarya but also in axons. As a result, axons appear red since they contain only MAP-tau while the dendrites and perikarya appear yellow, since they contain both proteins and the red and green signals superimpose to produce a yellow signal. DNA is shown in blue using theDAPI stain which highlights the nuclei. Image courtesyEnCor Biotechnology Inc.
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