Microtubule-associated protein 2 is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
in humans that is encoded by the ''MAP2''
gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
.
Function
This gene encodes a protein that belongs to the
microtubule-associated protein
In cell biology, microtubule-associated proteins (MAPs) are proteins that interact with the microtubules of the cellular cytoskeleton. MAPs are integral to the stability of the cell and its internal structures and the transport of components withi ...
family. The proteins of this family were originally isolated since they copurify with
tubulin
Tubulin in molecular biology can refer either to the tubulin protein superfamily of globular proteins, or one of the member proteins of that superfamily. α- and β-tubulins polymerize into microtubules, a major component of the eukaryotic cytosk ...
in polymerization experiments: tubulin in cell extracts can be made to polymerize to produce
microtubules (MT) under the influence of heat and the addition of
GTP, 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 by
SDS-PAGE
SDS-PAGE (sodium dodecyl sulfate–polyacrylamide gel electrophoresis) is a Discontinuous electrophoresis, discontinuous electrophoretic system developed by Ulrich K. Laemmli which is commonly used as a method to separate proteins with molecular m ...
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.
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 as
MAP Tau and
MAP1B. The MAP2 isoforms are thought to be involved in MT assembly, which is an essential step in
neuritogenesis. MAP2 serves to stabilize MT growth by crosslinking MT with
intermediate filaments and other MTs. MAP2 isoforms are neuron-specific
cytoskeletal proteins enriched in
dendrites and
perikarya, implicating a role in determining and stabilizing neuronal morphology during
neuron
A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...
development. As a result
antibodies
An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as bacteria and viruses, including those that caus ...
to MAP2 are widely used to identify neuronal cells and trace dendritic processes in experimental contexts.
Interactions
MAP2 has been shown to
interact with
Grb2
Growth factor receptor-bound protein 2, also known as Grb2, is an adaptor protein involved in signal transduction/ cell communication. In humans, the GRB2 protein is encoded by the ''GRB2'' gene.
The protein encoded by this gene binds recepto ...
,
NEFL
Neurofilament light polypeptide is a protein that in humans is encoded by the NEFL gene.
Structure
Neurofilament light polypeptide is a member of the intermediate filament protein family. This protein family consists of over 50 human proteins ...
and
MYO7A.
All MAP2 isoforms bind to microtubules.
333px, Neurons were grown in tissue culture and stained with antibody to MAP2 protein in green and MAP tau in red using the immunofluorescence technique. MAP2 is found only in dendrites and perikarya, while tau is found not only in the dendrites and perikarya but also in axons. As a result, axons appear red while the dendrites and perikarya appear yellow, due to superimposition of the red and green signals. DNA is shown in blue using the DAPI stain which highlights the nuclei. Image courtesy EnCor Biotechnology, EnCor Biotechnology Inc.
References
Further reading
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