Ah. Warner et al., POTENTIAL ROLE IN DEVELOPMENT OF THE MAJOR CYSTEINE PROTEASE IN LARVAE OF THE BRINE SHRIMP ARTEMIA-FRANCISCANA, Cell and tissue research, 282(1), 1995, pp. 21-31
Encysted embryos and larvae of the brine shrimp Artemia franciscana co
ntain a cysteine protease which represents over 90% of the protease ac
tivity in these organisms. We have used immunocytochemical methods to
determine the localization and potential role of the cysteine protease
in development of young larvae. In prenauplius larvae, there is inten
se staining for the protease on the basal side of the epidermal layer
in the posterior region and diffuse staining for the protease througho
ut the embryo. In first instar larvae, cysteine-protease staining beco
mes intense in the midgut-forming area where a reticulum-like pattern
emerges in cells with an abundance of yolk platelets. Cysteine-proteas
e staining in second instar larvae becomes intense in the apical side
of epidermal cells and in the basal and apical zones of midgut cells.
Subcellular localization of the protease in the epidermis and midgut o
f young larvae using immunogold electron microscopy suggests that most
is located in the cytosol and extracellular matrix adjacent to these
cells. Addition of cysteine-protease inhibitors to the growth medium,
especially the fluoromethyl ketone Z-Phe-Ala-CH2F, inhibits growth and
segmentation of the thorax. Collectively, these observations suggest
that the major cysteine protease in embryos and larvae functions in yo
lk utilization, as a hatching enzyme, in apolysis during the molt cycl
e, and as a digestive enzyme when the swimming larvae begin to feed.