Thioxothiazolidin derivative, 4‐OST, inhibits melanogenesis by enhancing the specific recruitment of tyrosinase‐containing vesicles to lysosome

Abstract

Tyrosinase catalyzes the rate‐limiting step in melanin synthesis. Melanin is synthesized from l‐tyrosin in the melanosomes, where tyrosinase and other melanogenic factors are recruited via the vesicle transport system. Genetic and biochemical approaches have revealed a correlation between impairments in the vesicle transport system and albinism. However, the specificity of the individual transport systems for the corresponding melanogenic factors has not been well elucidated yet. Here, we report that the thioxothiazolidin derivative, 4‐OST (4‐[(5E)‐5‐[(4‐fluorophenyl)methylidene]‐4‐oxo‐2‐sulfanylidene‐1,3‐thiazolidin‐3‐yl]‐4‐azatricyclo [5.2.1.02,6]dec‐8‐ene‐3,5‐dione: CAS RN. 477766‐87‐3) strongly inhibited melanogenesis in mouse melanoma B16F10 cells. 4‐OST reduces tyrosinase protein levels without affecting its messenger RNA levels or enzymatic activity. Although a reduction in tyrosinase protein level was observed in the presence of a protein synthesis inhibitor, the reduction may be coupled with protein synthesis. Similarly, GIF‐2202 (a derivative of 4‐OST) lowers tyrosinase protein levels without affecting the levels of another melanogenic enzyme, tyrosinase‐related protein 1 (TYRP1) level. The reduction in tyrosinase protein level is associated with an increase in the levels of the lysosomal proteinase cathepsin S. Chloroquine, a lysosome inhibitor, restored the tyrosinase protein level downregulated by GIF‐2202, although no effects of other inhibitors (against proteasome, autophagy, or exocytosis) were observed. In addition, GIF‐2202 segregated the immunofluorescence signals of tyrosinase from those of TYRP1. Chloroquine treatment resulted in co‐localization of tyrosinase and cathepsin S signals near the perinuclear region, suggesting that 4‐OST and GIF‐2202 may alter the destination of the tyrosinase vesicle from the melanosome to the lysosome. 4‐OST and GIF‐2202 can be new tools for studying the tyrosinase‐specific vesicle transport system.

GIF-2209, an Oxindole Derivative, Accelerates Melanogenesis and Melanosome Secretion via the Modification of Lysosomes in B16F10 Mouse Melanoma Cells

“…Lysosomes, marked by CD63, play an important role in melanogenesis. Therefore, we monitored the protein levels of melanogenic enzymes in the presence of the lysosome inhibitor chloroquine [ 8 ]. In the presence of 10 µM GIF-2209 and chloroquine, most cells were impaired (rounded) by 6 h. To alleviate cell impairment, the GIF-2209 concentration was decreased to 3 μM, and the incubation was shortened (24 h).…”

“…A number of small compounds that modulate melanogenesis have been reported and are categorized into several groups based on the mechanism of action, cellular signaling [ 4 , 5 ], transcription [ 6 ], translation [ 7 ], cellular trafficking [ 8 ], and degradation [ 9 ]. Post-translational modulators of melanogenic factors are often associated with intracellular trafficking and affect the maturation and fate of melanosomes and related organelles [ 10 ].…”

“…Large components, including organelles, are wrapped with an extra membrane (autophagosome) and fused with lysosomes, leading to autolysosomes. Melanogenic enzymes are also targets of lysosomes [ 16 ], and the inhibition of lysosomal activities by chloroquine and other pH neutralizers results in the accumulation of target molecules, including TYR [ 8 , 17 ]. Similar to impairments in the TYR enzyme, some small compounds that inhibit TYR activity accelerate the recruitment of the TYR enzyme to lysosomes.…”

“…However, it is known that lysosomal dysfunction ultimately impairs melanogenesis. The lysosome inhibitor chloroquine elevates the expression of TYR but suppresses melanogenesis [ 8 ]. Here, we report that GIF-2209, an oxindole derivative, upregulates melanogenesis.…”

The Bioactivity of Thiazolidin-4-Ones: A Short Review of the Most Recent Studies

“…Melanin is synthesized from L-tyrosine in melanosomes, where this process is controlled by many factors, including tyrosinase [32]. Isogawa et al showed that the rhodanine Derivative 17c (with 4-fluorobenzylidene substituent) strongly inhibited the melanogenesis process in mouse melanoma B16F10 cells in 10 µM concentration (Figure 9) [33]. Compound 17c reduced the level of tyrosinase activity without modifying its messenger RNA levels or enzymatic activity.…”