Ubiquitous macropinocytosis in anthozoans

Area of Science:

• Marine Biology
• Cell Biology
• Coral Physiology

Background:

• Transport mechanisms within coral tissues are not well understood.
• Previous studies have not fully documented how substances move from seawater into coral cells.

Purpose of the Study:

• To investigate the pathways of fluid, molecule, nutrient, and nanoparticle transport into and within coral tissues.
• To identify the primary cellular uptake mechanism in corals.

Main Methods:

• Tracking various tracers, including nanoparticles, in living coral animals.
• Utilizing inhibitors of phosphatidylinositol 3-kinase (PI3K) and actin polymerization to confirm cellular processes.
• Analyzing nanoparticle internalization dynamics based on size and tissue type.

Main Results:

• Nanoparticles enter coral tissues via the paracellular pathway after reaching the coelenteric cavity.
• Macropinocytosis is the primary mechanism for cellular uptake, forming large vesicles (350-600 nm) at the apical cell side.
• Uptake is size-dependent and varies among different coral tissues.
• Macropinocytosis is likely a significant endocytic pathway in other anthozoans.

Conclusions:

• Coral cells continuously internalize external medium via macropinocytosis, a process fundamental to nutrient and nanoparticle transport.
• This widespread cellular uptake mechanism challenges classical physiological models based on bilaterian studies.
• The findings suggest macropinocytosis plays a crucial role in coral 생태계 (ecosystem) interactions and nutrient acquisition.