WU, Su-Hua; LEE, Chi-Ying; National Changhua University of Education, Changhua, Taiwan, R.O.C; National Changhua University of Education, Changhua, Taiwan, R.O.C: Expression of crustacean hyperglycemic hormones in the hemocytes of the crayfish Procambarus clarkii

Crustacean hyperglycemic hormone (CHH) is a neurohormone originally identified in the X-organ sinus gland (XO-SG) of the eyestalk ganglia and primarily involved in the regulation of carbohydrate metabolism. Sequence analysis of CHHs isolated from various decapod crustaceans shows that they are peptides of 72-73 amino acid residues. The present study reports that CHH-like molecules are expressed in the hemocytes of the crayfish Procambarus clarkii. Significant levels of CHH-immunoreactivity were detected in the hemocyte extracts by a sandwich ELISA using antibodies against XO-SG CHH. Furthermore, three cDNA clones, dubbed TG/CG-CHH, Hem-CHH1, and Hem-CHH2, respectively, were identified using PCR-based cloning methods. Conceptual translation of these sequences revealed that TG/CG CHH encodes a typical CHH (72 residues) that shares a common sequence with the CHH first found in the crayfish cerebral and thoracic ganglia, whereas Hem-CHH1 and Hem-CHH2 each encodes a CHH-like peptide (40 residues) that is identical in sequence to the first 40 residues of the crayfish XO-SG and TG/CG CHH, respectively. Western blot analysis of hemocyte extracts also revealed the presence of CHH-immunoreactive bands. Separation of different types of hemocytes by density gradient centrifugation followed by RT-PCR using gene-specific primers implied a differential cellular expression of these hemocyte CHH-like molecules. The combined results not only show for the first time in any crustaceans that hemocytes express CHH-related molecules, but also add unique CHH variants to the existing repertoire of CHH molecular polymorphism. We postulate that these CHHs may play important roles in immune functions performed by the hemocytes.