Expression of constructs of the neuronal isoform of myosin-Va interferes with the distribution of melanosomes and other vesicles in melanoma cells.
Myosin-Va has been implicated in melanosome translocation, but the exact molecular mechanisms underlying this function are not known. In the dilute, S91 melanoma cells, melanosomes move to the cell periphery but do not accumulate in the tips of dendrites as occurs in wild-type B16 melanocytes; rather, they return and accumulate primarily at the pericentrosomal region in a microtubule-dependent manner. Expression of the full-length neuronal isoform of myosin-Va in S91 cells causes melanosomes to disperse, occupying a cellular area approximately twice that observed in non-transfected cells, suggesting a partial rescue of the dilute phenotype. Overexpression of the full tail domain in S91 cells is not sufficient to induce melanosome dispersion, rather it causes melanosomal clumping. Overexpression of the head and head-neck domains of myosin-Va in B16 cells does not alter the melanosome distribution. However, overexpression of the full tail domain in these cells induces melanosome aggregation and the appearance of tail-associated, aggregated particles or vesicular structures that exhibit variable degrees of staining for melanosomal and Golgi beta-COP markers, as well as colocalization with the endogenous myosin-Va. Altogether, the present data suggest that myosin-Va plays a role in regulating the direction of microtubule-dependent melanosome translocation, in addition to promoting the capture of melanosomes at the cell periphery as suggested by previous studies. These studies also reinforce the notion that myosin-V has a broader function in melanocytes by acting on vesicular targeting or intracellular protein trafficking.
da Silva Bizario
João Carlos
JC
Department of Molecular and Cellular Biology and Pathogenic Bioagents, Universidade de São Paulo, Faculdade de Medicina de Ribeirão Preto, Ribeirão Preto, Brazil.
da Cunha Nascimento
Alexandra Aparecida
AA
Casaletti
Luciana
L
Patussi
Eliana Valéria
EV
Chociay
Maria Fernanda
MF
Larson
Roy Edward
RE
Espreafico
Enilza Maria
EM
D000818:Animals; D000951:Antigens, Neoplasm; D001692:Biological Transport / Q000502:physiology; D015415:Biomarkers / Q000032:analysis; D018385:Centrosome / Q000502:physiology*; D020756:Coatomer Protein / Q000032:analysis; D005656:Fungal Proteins / Q000032:analysis; D058950:Melanoma-Specific Antigens; D020460:Melanosomes / Q000502:physiology*; D051379:Mice; D008870:Microtubules / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism*; D024701:Myosin Type V / Q000235:genetics / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000032:analysis; D009417:Nerve Tissue / Q000378:metabolism; D010641:Phenotype; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D014162:Transfection; D022161:Transport Vesicles / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D000951:Antigens, Neoplasm; D015415:Biomarkers; D020756:Coatomer Protein; D005656:Fungal Proteins; D058950:Melanoma-Specific Antigens; C513082:Myo5a protein, mouse; D009363:Neoplasm Proteins; D020033:Protein Isoforms; D024701:Myosin Type V; D018995:Myosin Heavy Chains