Two distinct, functionally independent adhesion mechanisms in marine sponges

Area of Science:

• Marine biology
• Cellular adhesion mechanisms
• Biochemistry

Background:

• Cells of multicellular organisms typically utilize complex adhesion systems.
• Marine sponges, specifically Geodia cydonium, possess unique Ca++-dependent adhesion mechanisms.
• Two distinct aggregation mechanisms, primary and secondary, have been identified in sponge cells.

Purpose of the Study:

• To investigate the molecular components and mechanisms underlying primary and secondary cell aggregation in Geodia cydonium.
• To identify and characterize the primary aggregation factor (pAF).
• To elucidate the roles of aggregation receptor (AR) and anti-aggregation receptor in controlling cell-cell interactions.

Main Methods:

• In vitro and in vivo experiments were conducted using the Geodia system.
• Isolation and characterization of the primary aggregation factor (pAF).
• Analysis of aggregation receptor (AR) binding capacity and interaction with other molecules.

Main Results:

• Secondary aggregation involves a complex of macromolecules, including UDP-glucuronosyltransferase and UDP-beta-D-galactosyltransferase.
• The aggregation receptor (AR) is a glycoprotein with D-glucuronic acid as the terminal sugar.
• The primary aggregation factor (pAF) is a bivalent, bifunctional glycoprotein firmly associated with the cell membrane.
• Cell aggregation and separation are regulated by AR binding capacity and an anti-aggregation receptor.

Conclusions:

• The initial aggregation of Geodia cells is mediated by a single-component system, the primary aggregation factor (pAF).
• Cell-cell adhesion in sponges involves intricate molecular interactions.
• Sponges exhibit transplantation immunopotentialities, opening new research avenues.