KIM, Hyun Woo; CHANG, Ernest S; MYKLES, Donald L; Colorado State University,Fort Collins,CO; Bodega Marine Lab, Bodega Bay,CA; Colorado State University, Fort Collins,CO: Effects of ecdysteroid on the expression of ecdysone receptor and three calpains in the land crab, Gecarcinus lateralis

Calpains constitute a large and diverse family of calcium-dependent cysteine proteinases. In decapod crustaceans, calpains mediate molt-induced claw muscle atrophy, in which selective degradation of myofibrillar proteins reduces muscle mass so that the claws are easily withdrawn at ecdysis. We isolated cDNAs encoding three calpain genes (Gl-Calpain A, Gl-Calpain B, and Gl-Calpain T) from land crab. The deduced 558-amino acid sequence of Gl-CalpA is most similar to lobster CalpM (Yu, X.L. & Mykles, D.L., 2003, J. Exp. Biol. 206:561-575). Gl-CalpB (754 amino acids) resembles Gl-CalpA, but has a calmodulin-like domain at the C-terminus. Gl-CalpT (639 amino acids) is most similar to the human type 5 calpain and C. elegans TRA-3. RT-PCR showed that CalpA and CalpB were expressed in most tissues, while CalpT was highly expressed in heart, thoracic muscle, and thoracic ganglion in intermolt animals. Using real-time RT-PCR, CalpB and CalpT mRNAs were increased up to 10-fold in limb regenerates. These results suggest that CalpB and CalpT are involved in tissue differentiation and growth. Animals were eyestalk-ablated to study the effects of elevated ecdysteroid hormones on gene expression in skeletal muscles. After 1 day post-ablation, there was no significant effect on expression of the three calpains in claw and thoracic muscles. However, ecdysone receptor (Gl-EcR) transcripts were increased claw muscle only, which suggests ecdysteroid regulates the changes in protein metabolism associated with molting. Supported by NSF (IBN-9904528).