Melanin protects skin against ultraviolet radiation-induced damage, thus reducing risk of cutaneous cancers. Our primary objective is to elucidate the mechanisms that regulate melanin synthesis and characterize the pathogenesis of pigmentary disorders. We will focus on tyrosinase, the enzyme that catalyzes the first, rate-limiting step in melanin synthesis, namely conversion of L-tyrosine to dihydroxyphenylalanine. Tyrosinase is a determinant of skin pigmentation and risk of cutaneous cancers. Tyrosinase has also been implicated in genetic disorders such as oculocutaneous albinism (OCA), in autoimmune diseases such as vitiligo, and in melanoma, and may be a modifier locus for primary congenital glaucoma and macular degeneration in X-linked retinoschisis. While tyrosinase activity varies as much as ten-fold in lightly versus darkly pigmented skin, mRNA and protein expression levels are remarkably similar. Instead, post-translational modification of tyrosinase is key for its regulation and activity. Disruption of tyrosinase folding has been implicated in 3 of the 4 major forms of OCA and may contribute to the immune response against melanocytes or melanoma.
In Specific Aim 1, we will elucidate the mechanisms underlying post-translational modification of tyrosinase and characterize the roles of the OCA-related proteins as well as protein chaperones in this process. We will also examine the effects of tyrosinase polymorphisms - such as those associated with vitiligo and melanoma risk - on protein folding and enzyme activity. OCA mutations cause accumulation of tyrosinase in the Endoplasmic reticulum (ER), triggering the unfolded protein response (UPR). We have shown that melanocytes adapt to sustained ER stress.
In Specific Aim 2, we will continue our investigation of the melanocyte UPR and determine how melanocytes evade apoptosis that is typical of sustained UPR activation. Recent studies suggest that UPR-modulating agents can increase the efficacy of chemotherapeutics. Understanding ER stress and the UPR in melanocytes may thus be critical in the design of adjuvants for melanoma therapies.
In Specific Aim 3, we will investigate and assess whether chemical chaperones that promote protein folding improve tyrosinase maturation, particularly in the absence of OCA-related proteins. Such compounds hold promise for the development of therapeutic agents for the OCAs. These studies will greatly advance our understanding of the regulation of skin pigmentation (a major risk factor for skin cancer) and pathogenesis of pigment disorders such as OCA and vitiligo.

Public Health Relevance

Tyrosinase is an enzyme essential for production of melanin that protects skin and eyes from ultraviolet radiation, for correct optic tract routing during development and has been implicated in the pathogenesis of albinism, vitiligo and skin cancers. In this study we will: (1) investigate post-translational modification of tyrosinase;(2) study activation of the unfolded protein response due to tyrosinase misfolding and subsequent adaptation to prevent melanocyte death;and (3) develop compounds that improve tyrosinase maturation for the treatment of albinism.

National Institute of Health (NIH)
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Research Project (R01)
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Arthritis, Connective Tissue and Skin Study Section (ACTS)
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Tseng, Hung H
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New York University
Schools of Medicine
New York
United States
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De Filippo, Elisabetta; Schiedel, Anke C; Manga, Prashiela (2017) Interaction between G Protein-Coupled Receptor 143 and Tyrosinase: Implications for Understanding Ocular Albinism Type 1. J Invest Dermatol 137:457-465
De Filippo, Elisabetta; Manga, Prashiela; Schiedel, Anke C (2017) Identification of Novel G Protein-Coupled Receptor 143 Ligands as Pharmacologic Tools for Investigating X-Linked Ocular Albinism. Invest Ophthalmol Vis Sci 58:3118-3126
Arowojolu, Omotayo A; Orlow, Seth J; Elbuluk, Nada et al. (2017) The nuclear factor (erythroid-derived 2)-like 2 (NRF2) antioxidant response promotes melanocyte viability and reduces toxicity of the vitiligo-inducing phenol monobenzone. Exp Dermatol 26:637-644
Manga, Prashiela; Elbuluk, Nada; Orlow, Seth J (2016) Recent advances in understanding vitiligo. F1000Res 5:
Murase, Daiki; Hachiya, Akira; Fullenkamp, Rachel et al. (2016) Variation in Hsp70-1A Expression Contributes to Skin Color Diversity. J Invest Dermatol 136:1681-1691
Doudican, Nicole A; Wen, Shih Ya; Mazumder, Amitabha et al. (2014) Identification of agents that promote endoplasmic reticulum stress using an assay that monitors luciferase secretion. J Biomol Screen 19:575-84
Cheng, Tsing; Orlow, Seth J; Manga, Prashiela (2013) Loss of Oca2 disrupts the unfolded protein response and increases resistance to endoplasmic reticulum stress in melanocytes. Pigment Cell Melanoma Res 26:826-34
Wang, Claire Q F; Akalu, Yemsratch T; Suarez-Farinas, Mayte et al. (2013) IL-17 and TNF synergistically modulate cytokine expression while suppressing melanogenesis: potential relevance to psoriasis. J Invest Dermatol 133:2741-2752
Toosi, Siavash; Orlow, Seth J; Manga, Prashiela (2012) Vitiligo-inducing phenols activate the unfolded protein response in melanocytes resulting in upregulation of IL6 and IL8. J Invest Dermatol 132:2601-9
Manga, Prashiela; Orlow, Seth J (2011) Informed reasoning: repositioning of nitisinone to treat oculocutaneous albinism. J Clin Invest 121:3828-31

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