Hauser F et al. (1990), Expression of spasmolysin (FIM-A.1): an integum...

XB-ART-25712

Exp Cell Res 1990 Aug 01;1892:157-62.

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Expression of spasmolysin (FIM-A.1): an integumentary mucin from Xenopus laevis.

Hauser F , Gertzen EM , Hoffmann W .

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In the past, a unique type of precursor for a secretory protein was discovered. It contains a central repetitive domain rich in threonine residues and terminal cysteine-rich domains. Due to striking homologies of these terminal domains with pancreatic spasmolytic polypeptide, originally the name "prepro-spasmolysin" was proposed. Here we show that the mature protein has a MW of about 130 kDa, consisting of about 70% carbohydrate and 30% protein. Similar O-linked glycoproteins have been found in mucins from human intestine. For this and numerous other reasons we decided to rename this glycoprotein "frog integumentary mucin A.1" (FIM-A.1). Furthermore, analysis of the protein with specific antibodies against the predicted C-terminal end indicates that FIM-A.1 is probably not processed at pairs of basic residues. In situ hybridization as well as immunofluorescence studies revealed that FIM-A.1 is expressed and stored exclusively in mature mucous glands of Xenopus laevis skin. Only cone cells at the proximal part of these glands do not synthesize FIM-A.1. In contrast, all other physiologically active peptides from X. laevis skin investigated so far are synthesized in granular glands. A hypothetical function of FIMs for defense against microbial infections is discussed.

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Species referenced: Xenopus laevis
Genes referenced: tff3.5

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	Fig.1 See image for captured text
	Fig. 2. See image for captured text
	FIG 3. immunohistochemical localization of spasmolysin (FIM-A.1) from dorsal X. Nevis skin. Immunofluorescence after treatment with preimmune serum (A) or antiserum SPL-5 (B). No immunoreactive material can be detected in granular glands (g) and vacuolated stages (v) of granular glands [19]. Arrows in (B) denote the positively stained mucin layer covering the epidermis. Scale bar, 100uM
	FIG. 4. Immunohistochemical analysis of mucous glands from dorsal X. laevis skin. (A) Immunofluorescence of a single gland after treatment with antiserum SPL-5. can be detected in the lumen of the gland as well as within granules of the epithelial cells but not in the cone cell at the proximal pole of the gland. Scale bar, 25 um. (B) Phase-contrast picture of (A). . (C) Immunofluorescence photomicrograph as in (A). e, Embryonic gland; m, mucous gland. Scale bar, 50 um.
	FIG 5. In situ hybridization of dorsal X. laevis skin. As a probe P32-labeled single-stranded cRNA (bamHI fragment from pUF1380) was used. Exposure time for autoradiography: 5days. (A) Dark field illumination representing positive signals indictating spasmolysin (FIM-A.l) mRNA solely at mucous gland cells; g, granular gland; m, mucous gland. (B) Phase-contrast picture. Scale bar, 100 um.
	Fig. 6. See image for captured text