MYO18A

Myosin-XVIIIa is a protein that in humans is encoded by the MYO18A gene.^[5][6] This protein is an unconventional myosin, which is an actin-based motor protein invoved in an array of intracellular processes, and myosin XVIIIa is characterized by the presence of an amino-terminal PDZ domain.^[7] This protein is ubiquitously expressed in tissues and is involved in vesicle trafficking and cytoskeletal organization.

MYO18A
Identifiers
Aliases	MYO18A, MYSPDZ, SPR210, myosin XVIIIA, MAJN, SP-R210
External IDs	OMIM: 610067; MGI: 2667185; HomoloGene: 7977; GeneCards: MYO18A; OMA:MYO18A - orthologs
Gene location (Human) Chr. Chromosome 17 (human)[1] Band 17q11.2 Start 29,071,122 bp[1] End 29,180,398 bp[1]
Gene location (Mouse) Chr. Chromosome 11 (mouse)[2] Band 11|11 B5 Start 77,763,246 bp[2] End 77,865,980 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in gastrocnemius muscle skeletal muscle tissue apex of heart muscle of thigh sural nerve right auricle of heart left ventricle corpus callosum right lobe of liver epithelium of colon Top expressed in muscle of thigh esophagus lip triceps brachii muscle ankle right ventricle temporal muscle skeletal muscle tissue intestinal villus neural layer of retina More reference expression data BioGPS n/a
Gene ontology Molecular function DNA binding nucleotide binding ADP binding actin filament binding ATPase activity protein binding ATP binding RNA binding Cellular component cytoplasm membrane trans-Golgi network actomyosin cytoskeleton myosin complex endoplasmic reticulum-Golgi intermediate compartment Golgi membrane Golgi apparatus cell surface Biological process Golgi organization Golgi vesicle budding actomyosin structure organization DNA metabolic process asymmetric Golgi ribbon formation negative regulation of apoptotic process positive regulation of protein secretion cell migration Golgi ribbon formation regulation of macrophage activation positive regulation of opsonization Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 399687 360013 Ensembl ENSG00000196535 ENSMUSG00000000631 UniProt Q92614 Q9JMH9 RefSeq (mRNA) NM_001346765 NM_001346766 NM_001346767 NM_001346768 NM_078471 NM_203318 NM_001291212 NM_001291213 NM_001291214 NM_001291215 NM_011586 RefSeq (protein) NP_001333694 NP_001333695 NP_001333696 NP_001333697 NP_510880 NP_976063 NP_001278141 NP_001278142 NP_001278143 NP_001278144 NP_035716 Location (UCSC) Chr 17: 29.07 – 29.18 Mb Chr 11: 77.76 – 77.87 Mb PubMed search [3] [4]
Wikidata
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This protein can also be found in literature as Molecule Associated with JAK3 N-terminus (MAJN), TGFB1-induced anti-apoptotic factor 1 (TIAF1), Myosin containing a PDZ domain (MYSPDZ), and Surfactant protein receptor SP-R210 (SP-R210).^[8][9]

Structure:

The MYO18a protein consists of 2,054 amino acids. This protein has a region (1-398) that mediates nucleotide-independent binding to F-actin and interaction with GOLPH3, a PDZ domain (220-311), an actin-interacting motif (114-118), a myosin motor domain (405-1185), an IQ domain (1188-1217), and has many alpha helical regions.^[9]

AlphaFold predicted structure for Myosin-XVIIIa, 70.69 average pLDDT

Isoforms:

This protein has 6 isoforms, designated a-f.

Function:

The myosin motor domain binds to ADP or ATP, but has no intrinsic ATPase activity. However, it does mediate ADP-dependent binding to actin.^[9] There is still a lack of evidence supporting the presence intrinsic motor activity in MYO18A protein.^[7]

This protein can bind GOLPH3, liking the Golgi apparatus to the cytoskeleton, participating in the tensile force required for vesicle budding from the Golgi, and influencing Golgi-to-plasma membrane trafficking. It could possibly give its flattened shape to the Golgi apparatus.^[10]

This protein is also part of a complex with LURAP1 (a scaffold protein) and CDC42BPA/CDC42BPB (proteins with kinase activity), whose function is modulating lamellar actomyosin retrograde flow, important in cell protrusion and migration.^[10][8]

Myosin-XVIIIa regulates the trafficking, expression, and activation of innate immune receptors on macrophages, and also aids in suppressing the inflammatory responsiveness of macrophages using a mechanism that modulates CD14 trafficking.^[11]

It also acts as a receptor of surfactant associated protein A (SFTPA1) and plays a large role in the internalization and clearance of SFTPA1-opsonized S. aureus by alveolar macrophages.^[12]It even enhances natural killer cell cytotoxicity.^[13]