Interactions of human myosin Va isoforms, endogenously expressed in human melanocytes, are tightly regulated by the tail domain

Westbroek W, Lambert J, Bahadoran P, Busca R, Herteleer MC, Smit N, Mommaas M, Ballotti R and Naeyaert JM
Source: J Invest Dermatol
Publication Date: (2003)
Issue: 120(3): 465-475
Research Area:
Dermatology/Tissue Engineering
Cells used in publication:
Melanocyte, (NHEM-Ad), human adult
Species: human
Tissue Origin: dermal
Primary human epidermal melanocytes express six endogenous isoforms of the human actin-accociated myosin Va motor protein. The authors studied the physiological role of this isoforms in human melanocytes. Therefore, several tail sequences were fused to GFP. Exon F in the C-terminal part of myosin Va is of major importance for association with melanosomes. The role of exon F was studied in regard to introcellular localization of myosin Va. Primary human melanocytes were transfected with two different myosin Va isoform (with/without exon F). Localization was determined by immuno-electron microscopy with anti-GFP antibody followed by protein A-gold incubation.
Primary human epidermal melanocytes express six endogenous isoforms of the human actin-associated myosin Va motor protein, involved in organelle transport. As isoforms containing exon F are most abundant in melanocytes, we hypothesized that these isoforms probably have a melanocyte-specific function. To uncover the biologic role of the six isoforms we introduced enhanced green fluorescent protein (eGFP)-myosin Va tail constructs in human melanocytes. We found that the medial tail, undergoing alternative splicing, has to be expressed in combination with the globular tail in order to obtain clear colocalization with organelles. Our data show that isoforms lacking exon F but containing exon D are associated with vesicles near the Golgi area. Myosin Va isoforms containing exon F are able to colocalize with and influence melanosome distribution by indirect interaction with rab27a and direct interaction with melanophilin. These results indicate that the myosin Va medial tail domain provides the globular tail domain with organelle-interacting specificity.