Mitf Involved in Innate Immunity by Activating Tyrosinase-Mediated Melanin Synthesis in Pteria penguin

Abstract

The microphthalmia-associated transcription factor (MITF) is an important transcription factor that plays a key role in melanogenesis, cell proliferation, survival and immune defense in vertebrate. However, its function and function mechanism in bivalve are still rarely known. In this research, first, a Mitf gene was characterized from Pteria penguin (P. penguin). The PpMitf contained an open reading frame of 1,350 bp, encoding a peptide of 449 deduced amino acids with a highly conserved basic helix-loop-helix-leucine zipper (bHLH-LZ) domain. The PpMITF shared 55.7% identity with amino acid sequence of Crassostrea gigas (C. gigas). Tissue distribution analysis revealed that PpMitf was highly expressed in mantle and hemocytes, which were important tissues for color formation and innate immunity. Second, the functions of PpMitf in melanin synthesis and innate immunity were identified. The PpMitf silencing significantly decreased the tyrosinase activity and melanin content, indicating PpMitf involved in melanin synthesis of P. penguin. Meanwhile, the PpMitf silencing clearly down-regulated the expression of PpBcl2 (B cell lymphoma/leukemia-2 gene) and antibacterial activity of hemolymph supernatant, indicating that PpMitf involved in innate immunity of P. penguin. Third, the function mechanism of PpMitf in immunity was analyzed. The promoter sequence analysis of tyrosinase (Tyr) revealed two highly conserved E-box elements, which were specifically recognized by HLH-LZ of MITF. The luciferase activities analysis showed that Mitf could activate the E-box in Tyr promoter through highly conserved bHLH-LZ domain, and demonstrated that PpMitf involved in melanin synthesis and innate immunity by regulating tyrosinase expression. Finally, melanin from P. penguin, the final production of Mitf-Tyr-melanin pathway, was confirmed to have direct antibacterial activity. The results collectively demonstrated that PpMitf played a key role in innate immunity through activating tyrosinase-mediated melanin synthesis in P. penguin.

Enhanced insulin‐regulated phagocytic activities support extreme health span and longevity in multiple populations

“…From there, eight of them were uniquely expressed among the innate professional phagocytes (Figure 5h , dash box), functioning as an interlinked regulatory network (Figure 5i ). While most of them revealed upregulated trends in Hainan LLIs, expression levels the microphthalmia‐associated transcription factor ( MITF ) which robustly regulate genes in the innate immune signaling pathways (Yu et al, 2021 ); the Kruppel‐like factor‐4 ( KLF4 ) that governs monocyte differentiation (Feinberg et al, 2007 ); and the activating transcription factor‐3 ( ATF3 ) that promotes macrophage migration and M2 polarization via suppressing the M1‐like fate (Sha et al, 2017 ) were only ones significantly induced (Figure 5j , Figure S12 ). Notably, these transcription factors were also direct targets of nuclear INSR, where robust binding sites were identified at their core promoter regions (Figure 5k ).…”

miRNA profiling of B16F10 melanoma cell exosomes reveals melanin synthesis-related genes

“…Tyrosinase plays a critical role in the synthesis of eumelanin, the most photoprotective black-brown melanin [ 34 ]. MITF protein plays a pivotal role in melanocyte lineage development and serves as a key transcription factor regulating the expression of tyrosinase and TYRP1 genes [ 18 ]. However, direct involvement of MITF in regulating melanin synthesis or the expression of endogenous tyrosinase or TYRP1 remains unproven.…”

“…We assessed the expression of mRNA related to melanin production in B16F10 cells after co-incubation with exosomes and found that the exosomes promote melanin production by increasing tyrosinase-related protein 1 (TYRP1) expression and decreasing microphthalmia-associated transcription factor (MITF) expression in the cells. Our finding is of particular interest since MITF is known to upregulate the expression of proteins involved in melanin synthesis, such as tyrosinase and TYRP1 [ 18 ]. We also conducted miRNA profiling of the exosomes and found the expression of many melanogenesis-related genes in the exosomes isolated from B16F10 cells.…”

MITF is a novel transcriptional regulator of the calcium sensor STIM1: Significance in physiological melanogenesis

“…The protein-DNA–binding specificity is provided by the basic region in protein and the key DNA interacting bases along with the flanking region. Most of the MITF-bound sites are CAGGTG “E-box” motifs flanked by A and/or T. This consensus “E-box” sequence is located in the promoter region of the MITF target genes like BCL2, tyrosinase, and cathepsin K (CTSK) ( 35 , 36 ). Interestingly, the genes involved in pigmentation have a specific “E-box” variant with a flanking T at the 5′ end of the core “E-box” motif.…”