Molecular characterization of an additional shrimp hyperglycemic hormone: cDNA cloning, gene organization, expression and biological assay of recombinant proteins

The crustacean eyestalk CHH/MIH/GIH neurohormone gene family represents a u nique group of neuropeptides identified mainly in crustaceans, In this stud y, we report the cloning and characterization of the cDNA and the gene enco ding the hyperglycemic hormone (MeCHH-B) of the shrimp Metapenaeus ensis. T he amino acid sequence of MeCHH-B shows 85% identity to that of MeCHH-A (fo rmerly MeCHH-like neuropeptide), Tno separate but identical MeCHH-B genes w ere identified in the genome of shrimp by library screening and they are lo cated on different CPM gene clusters, The organization of the MeCHH-B gene is identical to other members of the CHH/MIH/GIH neurohormone family. MeCHH -B is expressed at a constant level in the eyestalks of juveniles and matur e females. Unlike the MeCHH-A gene, a ion level of MeCHH-B transcripts can also be detected in the central nervous system. Interestingly, the expressi on pattern of MeCHH-B in the eyestalk of vitellogenic females is reversed t o that of the MeCHH-A gene. At the middle stage of gonad maturation, a mini mum level of MeCHH-B transcript was recorded and a maximum level of MeCHH-A transcript nas detected. Recombinant proteins for MeCHH-A and MeCHH-B were produced by a bacterial expression system. The hemolymph glucose level of bilaterally eyestalk-ablated shrimp increased two-fold 1 h after the rCHH i njection and then returned to normal after 2 h, The hyperglycemic effect of these fusion proteins is comparable to that of de-stalked shrimp injected with crude extract from a single sinus gland. (C) 2000 Federation of Europe an Biochemical Societies.