Fall 2009 Newsletter
Spring 2009 Newsletter
Fall 2008 Newsletter
Spring 2008 Newsletter
Our research concerns the regulation of molting and skeletal muscle plasticity in crabs and lobsters. Specific areas are signaling mechanisms in the molting gland and proteolytic mechanisms mediating molt-induced claw muscle atrophy. Quantitative methods are used to measure transcriptional and post-transcriptional regulation of signal transduction of molt-inhibiting hormone (MIH), a neuropeptide that inhibits ecdysteroid synthesis in the molting gland and myostatin, a TGFß superfamily member that induces skeletal muscle atrophy.
Signaling mechanisms in crustacean molting gland. Growth in crustaceans requires the periodic shedding of the shell, a process called molting, which is controlled by a neurosecretory center in the eyestalks. The complex secretes MIH that inhibits production of the molting hormone ecdysone, an ecdysteroid secreted by a pair of molting glands located in the body. Thus it appears that molting is triggered by a reduction in MIH in the blood, which stimulates the molting glands to synthesize and secrete ecdysone. It is thought that binding of MIH to a membrane receptor results in a cyclic nucleotide-dependent inhibition of ecdysone-synthesizing enzymes. Five genes were cloned in the tropical land crab that may play a role in MIH signaling: nitric oxide synthase (NOS), three guanylyl cyclases (GCs), and MIH. Proteomic approaches are used to identify and quantify levels and phosphorylation states of NOS and downstream targets of cyclic nucleotide-dependent protein kinases.
Regulation of muscle atrophy by myostatin. In mammals myostatin (Mstn) is a negative regulator skeletal muscle growth. We have recently identified Mstn orthologs in crabs and lobsters. As these genes are preferentially expressed in skeletal muscle, they may have similar functions in invertebrates. We have begun to examine the role of Mstn in controlling molt-induced claw muscle atrophy, in which the claw muscle mass is reduced as much as 78% before molting. The reduced mass facilitates withdrawal of the large claws through the narrow joints that connect the appendage to the body. Binding of Mstn to a membrane receptor results in phosphorylation of Smad proteins. Smads are transcription factors that translocate to the nucleus and alter gene expression. cDNAs encoding land crab Smads have been obtained. Quantitative RT-PCR and proteomic analysis will be used to measure Smad mRNA and protein levels, respectively. Image analysis will be used to quantify Smads in the nucleus and cytoplasm in response to Mstn.
Covi, J. A., Bader, B.D., Chang, E. S., and Mykles, D. L. (2009) Molt cycle regulation of protein synthesis in skeletal muscle of the blackback land crab, Gecarcinus lateralis, and the differential expression of a myostatin-like factor during atrophy induced by molting or unweighting. J. Exp. Biol., in press.
Mykles, D. L., Adams, M. E., Gäde, G., Lange, A. B., Marco, H. G., and Orchard, I. (2009) Neuropeptide action in insects and crustaceans. Physiol. Biochem. Zool., in press.
Kim, B. K., Kim, K. S., Oh, C. -W., Mykles, D. L., Lee, S.G., Kim, H.J., and Kim, H.-W. (2009) Twelve actin-encoding cDNAs from the American lobster, Homarus americanus: cloning and tissue expression of eight skeletal muscle, one heart, and three cytoplasmic isoforms. Comp. Biochem. Physiol. 153B: 178-184.
Covi, J. A., Chang, E. S., and Mykles, D. L. (2009) Conserved role of cyclic nucleotides in the regulation of ecdysteroidogenesis by the crustacean molting gland. Comp. Biochem. Physiol. 152A:470-477.
Zarubin, T. P., Chang, E. S., and Mykles, D. L. (2009) Expression of recombinant eyestalk crustacean hyperglycemic hormone from the tropical land crab, Gecarcinus lateralis, that inhibitsY-organ ecdysteroidogenesis in vitro. Mol. Biol. Rep. 36: 1231-1237.
Covi, J., Gomez, A., Chang, S., Lee, K., Chang, E., and Mykles, D. (2008). Repression of Y-organ ecdysteroidogenesis by cyclic nucleotides and agonists of NO-sensitive guanylyl cyclase. In: 4th Meeting of Comparative Physiologists & Biochemists in Africa - Mara 2008 - "Molecules to Migration: The Pressures of Life", Morris S. and Vosloo, A., eds. Medimond S.r.l., Monduzzi Editore International, Bologna, Italy, pp. 37-46.
Covi, J. A., Kim, H.-W., and Mykles, D. L. (2008) Expression of alternatively spliced transcripts for a myostatin-like protein in the blackback land crab, Gecarcinus lateralis. Comp. Biochem. Physiol. 150A:423-430.
