Abstract
The forkhead box protein P (FoxP) family members have been known to be important for regulation of immune responses in vertebrates, but their roles in invertebrate immunity remain unclear. In this study, a novel FoxP gene (LvFoxP) was identified from Pacific white shrimp Litopenaeus vannamei and functionally studied in the context of immune response. Possessing a conserved FoxP coiled-coil domain and a forkhead domain, LvFoxP shared homology to vertebrate FoxP family members, in particular FoxP1. Expression of LvFoxP was detectable in all the examined tissues and could be up-regulated by immune challenge in gill and hemocytes. The LvFoxP protein was present in both the cytoplasm and nucleus of hemocytes and could be nuclear-translocated upon immune stimulation. Silencing of LvFoxP increased the susceptibility of shrimp to infections by Vibrio parahaemolyticus and white spot syndrome virus (WSSV) and down-regulated the expression of multiple components of NF-κB and JAK-STAT pathways and almost all the examined immune effector genes. Moreover, the phagocytic activity of hemocytes from LvFoxP-silenced shrimp against V. parahaemolyticus was decreased. These suggested that LvFoxP could play a positive role in immune response. The current study may provide novel insights into the immunity of invertebrates and the functional evolution of the FoxP family.
Highlights
The Forkhead box (Fox) protein superfamily consists of a large group of transcriptional regulators with a forkhead/winged-helix DNA-binding domain, which are essentially implicated in regulation of development, homeostasis and metabolism [1, 2]
The constructed phylogenetic tree showed that the analyzed forkhead box protein P (FoxP) family proteins could be clustered into invertebrate and vertebrate categories, and LvFoxP was classified into the invertebrate group and most close to the putative LvFoxP1 and LvFoxP4 (Figure 2)
The expression of LvFoxP was activated after immune challenges with bacteria and virus, and the LvFoxP protein could be translocated into the nucleus upon immune stimulation
Summary
The Forkhead box (Fox) protein superfamily consists of a large group of transcriptional regulators with a forkhead/winged-helix DNA-binding domain, which are essentially implicated in regulation of development, homeostasis and metabolism [1, 2]. Mammalian FoxP family members generally function as transcriptional. Function of an Invertebrate FoxP repressors or activators involving in tumor suppression, development and, in particular, immunity [5]. FoxP3 plays critically roles in development and function of regulatory T cells (Tregs) by regulating expression of many genes and is identified as a classic marker for CD4+CD25+ Tregs [7]. FoxP1 and FoxP4 are well known to be involved in development and function of lymphatic cells [10, 11]. More and more sequences of the FoxP family member genes from various invertebrates have been deposited in Genbank database. Roles of the FoxP family in invertebrate immunity have not been explored so far
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