GPNMB is expressed in human epidermal keratinocytes but disappears in the vitiligo lesional skin

Arunasiri Iddamalgoda,Satoru Takayama,Lingli Yang,Aya Takahashi,Fei Yang,Yukiko Mizutani,Asako Ishitsuka,Ichiro Katayama,Kazal Boron Biswas,Shintaro Inoue

doi:10.1038/s41598-020-61931-1

Arunasiri Iddamalgoda, Satoru Takayama + Show 8 more

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https://doi.org/10.1038/s41598-020-61931-1

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Abstract

GPNMB is involved in multiple cellular functions including cell adhesion, stress protection and stem cell maintenance. In skin, melanocyte-GPNMB is suggested to mediate pigmentation through melanosome formation, but details of keratinocyte-GPNMB have yet to be well understood. We confirmed the expression of GPNMB in normal human epidermal keratinocytes (NHEKs) by reducing the expression using siRNA. A higher calcium concentration of over 1.25 mM decreased the GPNMB expression. Histological staining showed that GPNMB was expressed in the basal layer of normal skins but completely absent in vitiligo skins. The normal expression of GPNMB in nevus depigmentosus skin suggested that lack of GPNMB is characteristic of vitiligo lesional skins. IFN-γ and IL-17A, two cytokines with possible causal roles in vitiligo development, inhibited GPNMB expression in vitro. Approximately 4–8% of the total GPNMB expressed on NHEKs were released possibly by ADAM 10 as a soluble form, but the process of release was not affected by the cytokines. The suppressive effect of IFN-γ on GPNMB was partially via IFN-γ/JAK2/STAT1 signaling axis. Decreased GPNMB expression in keratinocytes may affect melanocyte maintenance or survival against oxidative stress although further studies are needed. These findings indicate a new target for vitiligo treatment, focusing on the novel role of IFN-γ and IL-17 in downregulating keratinocyte-GPNMB.

Highlights

GPNMB is involved in multiple cellular functions including cell adhesion, stress protection and stem cell maintenance
For normal human epidermal melanocytes (NHEMs), the specificity of the same antibody was proved by small-interfering RNA, which decreased GPNMB mRNA significantly (p < 0.01) (Supplementary Fig. S1b) with concomitant decreases of the signal corresponding to GPNMB in western blot (WB) (Supplementary Fig. S1c)
We began our study by verifying and validating the specificity of anti-GPNMB antibody in our own experimental systems using melanoma cells, as well as normal human epidermal melanocytes (NHEMs), a cell type in which GPNMB expression has been well characterized[1,19,28], as positive controls

Summary

Introduction

GPNMB is involved in multiple cellular functions including cell adhesion, stress protection and stem cell maintenance. Decreased GPNMB expression in keratinocytes may affect melanocyte maintenance or survival against oxidative stress further studies are needed. The known functions of GPNMB include cellular adhesion through integrin[1], regulation of the degeneration/regeneration of the extracellular matrix in skeletal muscles[6], the mineralization of bone[2], the differentiation of osteoclasts[8] and osteoblasts[9], the impairment of T-cell activation[10], the regulation of inflammatory responses in macrophages[11], the suppression of motor neuron degeneration in amyotrophic lateral sclerosis[12], and the invasion and metastasis of several cancers[13,14,15,16,17]. The extracellular fragments of GPNMB are known to be cleaved by a disintegrin and metalloproteases 10 (ADAM10) on the plasma membrane in the process of ectodomain shedding and secreted into the extracellular spaces[19] This shed GPNMB mediates signal transduction via cell surface proteins such as Na+/K+-ATPase[20]. The extracellular part of GPNMB has shown a neuroprotective property by attenuating astrocyte-mediated neuroinflammation in a CD44-dependent manner in mouse[21]

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