title: Proteasomal activities in the claw muscle tissue of European lobster, Homarus gammarus, during larval development.
abstract: Decapod crustaceans grow discontinuously and gain size through complex molt processes. The molt comprises the loss of the old cuticle and, moreover, substantial reduction and re-organization of muscles and connective tissues. In adult lobsters, the muscle tissue of the massive claws undergoes significant atrophy of 40-75% before ecdysis. The degradation of this tissue is facilitated by calcium-dependent proteases and by the proteasome, an intra-cellular proteolytic multi-enzyme complex. In contrast to the adults, the involvement of the proteasome during the larval development is yet not validated. Therefore, we developed micro-methods to measure the 20S and the 26S proteasomal activities within mg- and sub-mg-quantities of the larval claw tissue of the European lobster, Homarus gammarus. Within the three larval stages (Z1-3) we distinguished between sub-stages of freshly molted/hatched (post-molt), inter-molt, and ready to molt (pre-molt) larvae. Juveniles were analyzed in the post-molt and in the inter-molt stage. The trypsin-like, the chymotrypsin-like, and the peptidyl-glutamyl peptide hydrolase activity (PGPH) of the 20S proteasome increased distinctly from freshly hatched larvae to pre-molt Z1. During the Z2 stage, the activities were highest in the post-molt animals, decreased in the inter-molt animals and increased again in the pre-molt animals. A similar but less distinct trend was evident in the Z3 stages. In the juveniles, the proteasomal activities decreased toward the lowest values. A similar pattern was present for the chymotrypsin-like activity of the 26S proteasome. The results show that the proteasome plays a significant role during the larval development of lobsters. This is not only reflected by the elevated activities, but also by the continuous change of the trypsin/chymotrypsin-ratio which may indicate a shift in the subunit composition of the proteasome and, thus, a biochemical adjustment to better cope with elevated protein turnover rates during larval development.
authors.affiliation: Alfred Wegener Institute for Polar and Marine Research, Functional Ecology, PO Box 120161, 27515, Bremerhaven, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Götze
authors.forename: Reinhard
authors.initials: R
authors.lastname: Saborowski
mesh_terms: D000818:Animals; D007814:Larva / Q000502:physiology; D024510:Muscle Development; D018485:Muscle Fibers, Skeletal / Q000201:enzymology / Q000378:metabolism*; D009132:Muscles / Q000201:enzymology / Q000378:metabolism; D009133:Muscular Atrophy / Q000201:enzymology / Q000378:metabolism; D008121:Nephropidae / Q000254:growth & development* / Q000502:physiology*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*
chemical_list: D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease