Myosin V colocalizes with melanosomes and subcortical actin bundles not associated with stress fibers in human epidermal melanocytes.
Mutations of the gene encoding myosin V can produce a dilute or silvery hair color and various neurologic defects in mice and patients with Griscelli syndrome, leading to speculations that the myosin V motor protein plays a critical role in transporting melanosomes within melanocytes and neurosecretory vesicles within neurons. Therefore, we investigated the in vitro expression of myosin V in cultured normal human melanocytes, keratinocytes, and dermal fibroblasts using reverse transcriptase-polymerase chain reaction and northern blot analysis. Subcellular distribution of myosin V and proximity to actin bundles and melanosomes were determined by double indirect immunofluorescence labeling and immunogold electron microscopy. In all studied cells myosin V is expressed and treatment of melanocytes with the cyclic AMP-inducer 3-isobutyl-1-methylxanthine causes an induction of the myosin V message. In all cells myosin V colocalizes with actin bundles, concentrating in the subcortical cell zone. In the melanocyte it is closely associated with melanosomes. Quantitative analysis of myosin V labeling in melanocytes reveals a significantly higher (p < 0.005) presence of myosin V in the periphery of dendrites. These results suggest that myosin V is important in melanosome transport in human melanocytes. Possible roles in the other skin cells remain to be elucidated.
Lambert
J
J
Department of Dermatology, University Hospital, Gent, Belgium.
Onderwater
J
J
Vander Haeghen
Y
Y
Vancoillie
G
G
Koerten
H K
HK
Mommaas
A M
AM
Naeyaert
J M
JM
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000199:Actins / Q000378:metabolism*; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D003593:Cytoplasm / Q000201:enzymology; D003599:Cytoskeleton / Q000201:enzymology; D003713:Dendritic Cells / Q000166:cytology; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008544:Melanocytes / Q000378:metabolism*; D020460:Melanosomes / Q000378:metabolism*; D051379:Mice; D009218:Myosins / Q000235:genetics*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology
D000199:Actins; D010726:Phosphodiesterase Inhibitors; D009218:Myosins; D015056:1-Methyl-3-isobutylxanthine