Increasing Intercellular Communication and Directional Organelle Transfer in Oyster Hemocytes under Copper Stress

Copper (Cu) is a common marine pollutant and can impair many physiological processes in the innate immune systems of invertebrates. Tunneling nanotubes (TNTs) are a novel route of intercellular communication in mammalian cells, but their important roles in invertebrate immunocytes are unknown. Bivalve hemocytes are unique and sensitive innate immune systems comprising different subpopulations with various functions. In this study, we, for the first time, demonstrated that Cu caused an increased formation of TNTs with elongation to facilitate the intercellular communication. Surprisingly, directional mitochondria transfer was induced under Cu stress from low to high phagocytic subpopulations via TNTs, which provided an enhanced energy and phagocytic function of granular hemocytes. Despite its low proportion, agranulocytes played a vital role in intercellular communication, and granulocytes were impaired in cell-to-cell communication under Cu exposure. These results revealed a new and novel cell survival strategy by directional organelle transfer in stressful environments.