D-galactose binding lectins from the tunicate Ascidia malaca: subunit characterization and hemocyte surface...

Area of Science:

• Marine Biology
• Biochemistry
• Immunology

Background:

• Ascidia malaca serum contains D-galactose specific lectins.
• These lectins are major protein components with a molecular weight of approximately 58,000 daltons.
• Intramolecular disulfide linkages suggest a compact protein structure for these lectins.

Purpose of the Study:

• To investigate the presence and characteristics of D-galactose specific lectins in Ascidia malaca.
• To determine if these lectins are also present on the surface of hemocytes.
• To explore the similarities between serum lectins and hemocyte-associated lectins.

Main Methods:

• Purification of D-galactose specific lectins from Ascidia malaca serum.
• Analysis of protein component molecular weight and behavior under reducing/non-reducing conditions.
• Immunofluorescence microscopy to detect lectins on hemocyte surfaces.
• Sepharose spherule binding assays and rosette formation with erythrocytes.
• Inhibition assays using specific sugars.
• Hemagglutination assays using antibodies against serum lectins.

Main Results:

• A major protein component of ~58,000 daltons was identified in Ascidia malaca serum lectins.
• D-galactose specific lectins were detected on the surface of approximately 34% of Ascidia malaca hemocytes.
• Hemocyte-bound lectins showed specific binding to Sepharose spherules and formed rosettes with erythrocytes, inhibitable by specific sugars.
• Antibodies to serum lectins induced hemocyte agglutination.

Conclusions:

• Evidence supports the hypothesis that D-galactose specific lectins exist both free in the serum and on the surface of Ascidia malaca hemocytes.
• These serum and cell-surface lectins share similar specificities and structural characteristics.
• The findings suggest a potential dual role for these lectins in Ascidia malaca immune responses.