MAP1-family proteins are microtubule-associated proteins (MAPs) that bind along the microtubule lattice. Mammalian genomes usually contain three family members, MAP1A, MAP1B and MAP1S. Only one family member, Futsch, is found in Drosophila.Human MAP1A and MAP1B, are predominantly expressed in neurons, where they are thought to be important in the formation and development of axons and dendrites [, ]. Human MAP1A and MAP1B stabilise microtubules and interact with other cellular components, including filamentous actin and signalling proteins. The activity of MAP1A and MAP1B is controlled by upstream signalling mechanisms, including the MAP kinase and glycogen synthase kinase-3 beta pathways []. This entry represent MAP1B. It may bind to at least two tubulin subunits in the polymer. This bridging of subunits might be involved in nucleating microtubule polymerisation and in stabilising microtubules []. Besides its microtubule regulation functions, MAP1B also acts as a signalling protein involved in normal physiology and pathological conditions in the nervous system [].
MAP1 is one of the first described microtubule-associated proteins (MAPs). It was discovered through its association with tubulin, and was later resolved into three distinct proteins: MAP1A, MAP1B (also called MAP5) and MAP1C. MAP1A and MAP1B are structurally related and share light chains with each other, and MAP1C was later shown to be the heavy chain of brain cytoplasmic dynein [].MAP1A is a long, rod-shaped protein that is made up of a large heavy chain and three light chains, LC1, LC2 and LC3. Light chain binding appears to regulate the activity of MAP1A and MAP1B []. MAP1A binds to and stabilises microtubules and can promote microtubule assembly []. It is expressed in mature neurons and may serve a key function in synaptic plasticity [, ].
The Drosophila protein Futsch has homology to MAP1B and controls synaptic growth at the Drosophila neuromuscular junction through the regulation of the synaptic microtubule cytoskeleton. Futsch protein colocalises with microtubules and identifies cytoskeletal loops that traverse the lateral margin of select synaptic boutons. Futsch mutations disrupt synaptic microtubule organisation, reduce bouton number, and increase bouton size. These deficits can be partially rescued by neuronal overexpression of a Futsch MAP1B homology domain []. The translation of Futsch is repressed by fragile X messenger ribonucleoprotein 1 (FMR1/FMRP), an RNA binding protein that acts as a negative translational regulator []. The N- and C-terminal domains of Futsch are homologous to the vertebrate MAP1B microtubule-associated protein. The central domain of Futsch is highly repetitive []. This entry represents the Futsch repeats.
MAP1-family proteins are microtubule-associated proteins (MAPs) that bind along the microtubule lattice. Mammalian genomes usually contain three family members, MAP1A, MAP1B and MAP1S. Only one family member, Futsch, is found in Drosophila.Human MAP1A and MAP1B, are predominantly expressed in neurons, where they are thought to be important in the formation and development of axons and dendrites []. Human MAP1A and MAP1B stabilise microtubules and interact with other cellular components, including filamentous actin and signaling proteins. The activity of MAP1A and MAP1B is controlled by upstream signaling mechanisms, including the MAP kinase and glycogen synthase kinase-3 beta pathways []. Human MAP1S is a heterodimer with a heavy and a light chain. Both MAP1S heavy and light chains interact with microtubules, while MAP1S light chain interacts with actin []. MAP1S is involved in the formation of microtubule bundles []. It mediates aggregation of mitochondria resulting in cell death and genomic destruction (MAGD) []. It bridges autophagic components with microtubules and mitochondria plays a role in apoptosis [, , ].
In microtubule-associated protein 1B (MAP1B) the basic region containing the KKEE and KKEVI motifs is responsible for the interaction between MAP1B and microtubules in vivo. This region bears no sequence relationship to the microtubule binding domains of kinesin, MAP2, or tau [].Neuraxin is a putative structural protein of the rat central nervous system that is immunologically related to microtubule-associated protein 5 (MAP5). Neuraxin may be implicated in neuronal membrane-microtubule interactions [].Both proteins contain a region that consists of 12 tandemrepeats of a 17 residues motif.
MAP1-family proteins are microtubule-associated proteins (MAPs) that bind along the microtubule lattice. Mammalian genomes usually contain three family members, MAP1A, MAP1B and MAP1S. Only one family member, Futsch, is found in Drosophila.Human MAP1S is a heterodimer with a heavy and a light chain. Both MAP1S heavy and light chains interact with microtubules, while MAP1S light chain interacts with actin []. Unlike MAP1A and MAP1B, MAP1S is expressed in a wide range of tissues in addition to neurons []. MAP1S serves as a linker to connect mitochondria with microtubules for trafficking, and to bridge the autophagy machinery with microtubules and mitochondria to affect autophagosomal biogenesis and degradation [, , , ]. In mice, MAP1S may enhance autophagy to suppress genomic instability and tumorigenesis [].
