Olfactory specific chymotrypsin-like serine protease from the aesthetasc tegumental gland of the lobster, Homarus americanus
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Numerous proteases and protease inhibitors are expressed in the lobster olfactory organ. One of these proteases, olfactory enriched transcript 03 (OET-03), is particularly interesting because its mRNA is expressed only in one cell type of the olfactory organ of the American lobster, Homarus americanus. We have obtained a full-length cDNA clone of OET-03. The predicted amino acid sequence is equally divided between a novel N-terminal domain and a conserved serine protease catalytic domain at the C-terminus. Heterologous expression in HEK293 cells allowed protease assays demonstrating that OET-03 cleaved a specific serine protease substrate, N-alpha benzoyl-L-arginine p-nitroanilide, but did not cleave a substrate of metalloproteases and cysteine proteases. OET-03 protease activity was significantly inhibited by the chymotrypsin-like protease inhibitor, tosyl-L-phenylalanine chloromethyl ketone, but not by the general protease inhibitor, phenylmethylsulfonyl fluoride. Immunoreactivity for OET-03 was detected only in the cells previously shown to contain OET-03 mRNA. The cytoplasm of these cells was filled with enlarged smooth endoplasmic reticulum (a characteristic of secretory cells) that appeared to expand into large electron-translucent areas at the ventral end of the cell. The ventral ends of these secretory cells were apposed to phalloidin-labeled triangular structures reminiscent of the beginnings of the ducts of crustacean tegumental glands. This putative gland was found only in association with the aesthetasc sensory units of the olfactory organ, hence the name, aesthetasc tegumental gland.
KeywordsSecretion Proteolysis Smell Aesthetasc tegumental gland American lobster, (Homarus americanus (Crustacea))
We thank Dr. Bruce Maley, Dr. Charles Derby and Dr. Manfred Schmidt for helpful discussions.
- Alexander CG (1989) Tegumental glands in the paragnaths of the Palaemon serratus (Crustacea: Natantia). J Mar Biol Assoc UK 69:53–63Google Scholar
- Derby CD, Schmidt M (2005) Exocrine glands containing serine protease are associated with olfactory sensilla in the Spiny lobster, Panulirus argus. Chem Senses (in press)Google Scholar
- Mauchline J (1977) The integumental sensilla and glands of pelagic crustacea. J Mar Biol Assoc UK 57:973–994Google Scholar
- Rittschof D (1993) Body odors and neutral-basic peptide mimics: a review of responses by marine organisms. Am Zool 33:487–493Google Scholar
- Shyamasundari K, Rao KH (1978) Studies on the Indian sand lobster Thenus orientalis (Lund): mucopolysaccharides of the tegumental glands. Folia Histochem Cytochemica 16:247–254Google Scholar
- Stevenson JR (1985) Dynamics of the integument. In: Bliss DE, Mantel LH (eds) The biology of crustacea, vol 9. Academic, Orlando, pp 1–42Google Scholar
- Talbot P, Demers D (1993) Tegumental glands of Crustacea. In: Horst NH, Freeman JA (eds) The crustacean integument morphology and biochemistry. CRC, Ann Arbor, pp 152–191Google Scholar
- Yonge CM (1932) On the nature and permeability of chitin. I. The chitin lining the foregut of decapod Crustacea and the function of the tegumental glands. Proc R Soc Lond [Biol] 111:298–329Google Scholar