SYT14L, especially its C2 domain, is involved in regulating melanocyte differentiation.
ABSTRACT The formation of dendrites by melanocytes is highly analogous to that process in neural cells. We previously reported that a C2 domain-containing protein, copine-1, is involved in the extension of dendrites by neural cells. However, the effect of C2 domain-containing proteins in dendrite formation by melanocytes has not yet been elucidated.
The aim of this study was to screen novel C2 domain-containing proteins related to dendrite outgrowth in melanocytes and to investigate their precise roles in melanocyte dendrite formation during differentiation.
We transduced mouse melan-a melanocytes with a recombinant adenovirus expressing a C2 domain library. Dendrite elongation, melanin content, tyrosinase activity and Western blot analyses were conducted to elucidate the possible underlying mechanisms of action in melanocytes.
Sixteen sets of C2 domain-containing proteins were identified whose over-expression resulted in dendrite lengthening. Among those, we focused on the C2 domain of SYT14L (truncated mutant of SYT14L) in this study. Forced expression of full length SYT14L or the C2 domain of SYT14L induced a significant elongation of dendrite length accompanied by the induction of melanocyte differentiation-related markers, including melanin synthesis, tyrosinase catalytic activity and the expression of tyrosinase (TYR), tyrosinase related protein-1 (TRP-1) and TRP-2. In addition, over-expression of either the C2 domain or the full length form of SYT14L significantly increased the phosphorylation of ERK and CREB.
These results suggest that SYT14L, especially its C2 domain, may play an important role in regulating melanocyte differentiation through the modulation of ERK and (or) CREB signaling.
- [show abstract] [hide abstract]
ABSTRACT: REGULATION of pigmentation is of considerable importance throughout the animal kingdom. Photoprotection, social behaviour, and a number of disorders like albinism, vitiligo, and melanoma are affected by the amount and distribution of melanin in the organism. Melanin is synthesised in melanosomes beginning with the oxidation of tyrosine to dihydroxy-phenyalanine (DOPA) by the enzyme tyrosinase. In Cloudman S91 melanoma cells, tyrosinase activity and melanisation are stimulated by elevated intracellular levels of cyclic AMP1, apparently through the inactivation of an inhibitor of tyrosinase2. We initiated a series of experiments to identify the molecules controlling tyrosinase activity. Kuo and Greengard's observations on the widespread occurrence of cyclic AMP-dependent protein kinases throughout the phyla suggested that protein phosphorylation reactions might be involved3. We describe here a cell-free system in which tyrosinase is activated following the addition of a cyclic AMP-dependent protein kinase isolated from melanoma cells. The kinetics of the reaction in the cell-free system are similar to those in intact cells. The activation of tyrosinase is completely dependent on the protein kinase and is enhanced by cyclic AMP, ATP, and magnesium. The activation involves the removal of an inhibitor of tyrosinase; in addition, a phosphoprotein phosphatase is present which is distinct from the inhibitor but which appears to antagonize the kinase-mediated reaction.Nature 07/1977; 267(5610):444-7. · 38.60 Impact Factor