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SUMMARY:**PhD Seminar** Effect of molting hormones (ecdysteroids) on myosta
 tin and mTOR expression in skeletal muscle and limb regenerates in the bla
 ckback land crab, Gecarcinus lateralis
LOCATION:Yates 206
TZID:America/Denver
DTSTART:20151201T000000
UID:2026-05-13-07-51-15@natsci.colostate.edu
DTSTAMP:20260513T075115
Description:&nbsp\;\n\nDuring premolt\, increasing ecdysteroid levels cause
  claw muscle atrophy in Gecarcinus lateralis\, allowing withdrawal of the 
 claw at ecdysis. Myostatin (Gl-Mstn) is negatively correlated to ecdystero
 ids\, while protein synthesis is up-regulated to allow myofibril remodelin
 g during premolt. In mammals\, glucocorticoids inhibit mechanistic Target 
 of Rapamycin (mTOR)-dependent protein synthesis. Our hypothesis is that ec
 dysteroids inhibit Gl-Mstn expression through the ecdysteroid receptor. Gl
 -Mstn\, in turn\, inhibits protein synthesis via mTOR signaling. Using DNA
  walking\, an ecdysteroid receptor response element (EcRE) was located nea
 r the 5’ end of the Gl-Mstn promoter\, suggesting that Gl-Mstn expressio
 n is directly regulated by ecdysteroids. Limb bud autotomy\, which suspend
 s premolt by lowering hemolymph ecdysteroids levels\, decreased Gl-EF2\, G
 l-Rheb\, Gl-mTOR and Gl-S6K mRNA in LBs\, increased Gl-Mstn expression in 
 claw muscle\, and had no effect on these genes in thoracic muscle. After o
 ne week of daily 20-hydroxyecdysone injections of intermolt animals\, Gl-R
 heb mRNA levels were significantly increased in claw muscle\, but Gl-Mstn 
 mRNA level was unchanged. These results indicated a difference in response
  to ecdysteroids between intermolt and premolt tissues. The Gl-Mstn promot
 er was fused to luciferase and transfected into HeLa cells\, along with Uc
 a pugilator EcR (Up-EcR) and Up-RXR\, to determine whether the EcRE is fun
 ctional. Ecdysteroids had no effect on expression of the reporter gene in 
 HeLa cells. The data suggest that Gl-Mstn expression is regulated by ecdys
 teroids. However\, there was no consistent linkage between expression of G
 l-Mstn and expression of mTOR signaling components in claw and LB muscles.
  4:00 pm
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