β-Thymosins and Hemocyte Homeostasis in a Crustacean

Abstract

Thymosin proteins are well known for their actin-binding activity. Thymosin beta 4 (Tβ4) has been associated with biological activities in tissue repair and cell migration via interaction with ATP-synthase in vertebrates, while the information of similar thymosin functions in invertebrates is limited. We have shown previously that ATP-synthase is present on the surface of crayfish hematopoietic tissue (HPT) cells, and that astakine 1 (Ast1, an invertebrate cytokine) was found to interact with this β-subunit of ATP synthase. Here, we identified five different β-thymosins from Pacifastacus leniusculus, designated Pl-β-thymosin1-5. The two dominant isoforms in brain, HPT and hemocytes, Pl-β-thymosin1 and 2, were chosen for functional studies. Both isoforms could bind to the β-subunit of ATP-synthase, and Pl-β-thymosin1, but not Pl-β-thymosin2, significantly increased extracellular ATP formation. Moreover, Pl-β-thymosin1 stimulated HPT cell migration in vitro and Ast1 blocked this effect. Pl-β-thymosin2 increased the circulating hemocyte number at an early stage after injection. Additionally, in vivo injection of Pl-β-thymosin1 resulted in significant reduction of reactive oxygen species (ROS) production in crayfish HPT whereas Pl-β-thymosin2 had a similar but transient effect. Both Pl-β-thymosins induced the expression of Ast1 and superoxide dismutase (SOD) transcripts, while silencing of endogenous Pl-β-thymosin 1 and 2 by RNAi resulted in significant reduction of the Ast1 and SOD transcripts. The diverse effects exhibited by Pl-β-thymosin1 and Pl-β-thymosin2 indicates that these proteins are involved in a complex interaction that regulates the hematopoietic stem cell proliferation and differentiation.

Molecular characteristics of three thymosin-repeat proteins from Marsupenaeus japonicus and their responses to WSSV infection

“…The results indicated that mjthm4, mjthm3, and mjthm2 might have arisen from the same transcript through alternative splicing. A similar phenomenon has also been found in other crustaceans (Gai et al, 2009;Saelee et al, 2013;Shi et al, 2015). Then, the transcript profiles revealed that mjthm4, mjthm3, and mjthm2 are important for the digestive tracts to fulfill their functions, such as nutrition absorption and pathogen defense.…”

“…In contrast, invertebrates such as Acanthamoeba Actobindin (Vancompernolle et al, 1991), Hydra Thypedin (Herrmann et al, 2005), Caenorhabditis Tetra Thymosinβ (Van Troys et al, 2004), Hermissenda Csp24 (Crow and XueBian, 2000), Eriocheir EsTRP1 and EsTRP2 (Gai et al, 2009), and Drosophila Cibulout (Boquet et al, 2000), Procambarus clarkia PcThy-1 to PcThy-1 (Shi et al, 2015), usually have β-thymosins with multi-β-thymosin domains. These β-thymosins have mainly contributed to brain metamorphosis (Boquet et al, 2000), foot regeneration (Herrmann et al, 2005), antimicrobial processes, wound-healing and tumor growth (Gai et al, 2009), neuronal development (Crow and Xue-Bian, 2000), hematopoietic stem cell proliferation and differentiation (Saelee et al, 2013), antiviral immunity (Shi et al, 2015), and actin binding.…”

A thymosin beta-4 is involved in production of hemocytes and immune defense of Hong Kong oyster, Crassostrea hongkongensis

“…They remove damaged cells and tissue debris from the wound area by phagocytosis (Ottaviani et al, 1996). During the wound healing, Tβ4 could greatly promote hemocytes migration, which will facilitate the wound healing (Saelee et al, 2013). As a result, a tissue injury experiment was conducted to investigate the potential role of ChTβ4 during wound healing.…”

Echinoderm Antimicrobial Peptides to Contrast Human Pathogens

“…β-Thymosin is also described as one of the AMP of platelets from animals and human beings [29]. There is little information about the function of thymosins in invertebrates, but their presence has been reported in marine invertebrates [30,31] and in insects where they are up regulated by microbial infections [32].…”