Effects of abalone (Haliotis discus hannai Ino) gonad polysaccharides on cholecystokinin release in STC-1 cells and its signaling mechanism

• Sulfated polysaccharides, AGP-31, 32 and 33 were purified from abalone gonad.
• AGPs have similar monosaccharide profile but different molecular weights.
• All the AGPs could significantly increase the secretion of CCK in STC-1 cells.
• Ca2+/CaM/CaMK, cAMP/PKA and MAPK pathways are involved in CCK secretion by AGPs.

Abalone gonad polysaccharide (AGP) −31, −32 and −33 prepared in this study had the molecular weight (MW) of 37.8, 32.2 and 27.5 kDa, respectively. They all contained mannose, rhamnose, glucuronic acid, glucose, galactose, xylose, arabinose, and fucose, with very similar monosaccharide profile. All the three polysaccharides could significantly increase the secretion of cholecystokinin (CCK) in STC-1 cells. Among them, AGP-32 showed the strongest effect. However, the low-MW fragments of AGP-32 showed significantly lower activity than AGP-32 itself. It was also found that the inhibitors on calcium-sensing receptor (CaSR), protein kinase A (PKA), Ca2+⁄calmodulin-dependent protein kinase (CaMK) II, p38- mitogen-activated protein kinases (MAPK), and an intracellular calcium chelator all inhibited AGP-induced CCK secretion. To conclude, Ca2+/calmodulin (CaM)/CaMK, cyclic adenosine monophosphate (cAMP)/PKA and MAPK pathways are all involved in AGP-induced CCK secretion.