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Evidence for the occurrence of membrane-type serine protease 1/matriptase on the basolateral sides of enterocytes.

ABSTRACT: MT-SP1 (membrane-type serine protease 1)/matriptase is an epithelial-derived integral membrane enzyme. The purpose of the present study was to examine whether the enzyme exists on the basolateral side of simple columnar epithelial cells, such as enterocytes, of normal adult animals. Using COS-1 monkey kidney cells transiently transfected with rat MT-SP1/matriptase expression plasmids, we found that the enzyme is post-translationally processed by the cleavage between Gly149 and Ser150, that a portion of the C-terminal part (Ser150-Val855) remains in the cells by association with the NTF (N-terminal fragment) (Met1-Gly149), while the other portions are released into the medium and that the release is increased on activation by co-expression with hepatocyte growth factor activator inhibitor type-1. Western-blot analysis of crude membranes prepared from rat jejunum demonstrated the presence of the NTF but negligible or no occurrence of the C-terminal part of the protein. Fractionation of the crude membranes by ultracentrifugation with Percoll followed by Western-blot analysis showed that the fractionation profile of the NTF correlated significantly with that of E-cadherin, an adhesion molecule on the lateral membrane. Immunostaining of the jejunum demonstrated the occurrence of the NTF on the lateral membranes but not on the apical membranes. These results suggest that considerable MT-SP1/matriptase molecules occur on the basolateral sides of normal epithelial cells and support our hypothesis that a possible physiological function of this enzyme is the control of epithelial-cell turnover by regulating cell-cell and/or cell-substratum adhesions.

SUBMITTER: Tsuzuki S

PROVIDER: S-EPMC1138976 | biostudies-literature | 2005 Jun

REPOSITORIES: biostudies-literature

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Evidence for the occurrence of membrane-type serine protease 1/matriptase on the basolateral sides of enterocytes.

Tsuzuki Satoshi S Murai Nobuhito N Miyake Yuka Y Inouye Kuniyo K Hirayasu Hirofumi H Iwanaga Toshihiko T Fushiki Tohru T

The Biochemical journal 20050601 Pt 2

MT-SP1 (membrane-type serine protease 1)/matriptase is an epithelial-derived integral membrane enzyme. The purpose of the present study was to examine whether the enzyme exists on the basolateral side of simple columnar epithelial cells, such as enterocytes, of normal adult animals. Using COS-1 monkey kidney cells transiently transfected with rat MT-SP1/matriptase expression plasmids, we found that the enzyme is post-translationally processed by the cleavage between Gly149 and Ser150, that a por ...[more]

PMID: 15669920

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Project description:PURPOSE:Matriptase-2 (also known as TMPRSS6) is a critical regulator of the iron-regulatory hormone hepcidin in the liver; matriptase-2 cleaves membrane-bound hemojuvelin and consequently alters bone morphogenetic protein (BMP) signaling. Hemojuvelin and hepcidin are expressed in the retina and play a critical role in retinal iron homeostasis. However, no information on the expression and function of matriptase-2 in the retina is available. The purpose of the present study was to examine the retinal expression of matriptase-2 and its role in retinal iron homeostasis. METHODS:RT-PCR, quantitative PCR (qPCR), and immunofluorescence were used to analyze the expression of matriptase-2 and other iron-regulatory proteins in the mouse retina. Polarized localization of matriptase-2 in the RPE was evaluated using markers for the apical and basolateral membranes. Morphometric analysis of retinas from wild-type and matriptase-2 knockout (Tmprss6(msk/msk) ) mice was also performed. Retinal iron status in Tmprss6(msk/msk) mice was evaluated by comparing the expression levels of ferritin and transferrin receptor 1 between wild-type and knockout mice. BMP signaling was monitored by the phosphorylation status of Smads1/5/8 and expression levels of Id1 while interleukin-6 signaling was monitored by the phosphorylation status of STAT3. RESULTS:Matriptase-2 is expressed in the mouse retina with expression detectable in all retinal cell types. Expression of matriptase-2 is restricted to the apical membrane in the RPE where hemojuvelin, the substrate for matriptase-2, is also present. There is no marked difference in retinal morphology between wild-type mice and Tmprss6(msk/msk) mice, except minor differences in specific retinal layers. The knockout mouse retina is iron-deficient, demonstrable by downregulation of the iron-storage protein ferritin and upregulation of transferrin receptor 1 involved in iron uptake. Hepcidin is upregulated in Tmprss6(msk/msk) mouse retinas, particularly in the neural retina. BMP signaling is downregulated while interleukin-6 signaling is upregulated in Tmprss6(msk/msk) mouse retinas, suggesting that the upregulaton of hepcidin in knockout mouse retinas occurs through interleukin-6 signaling and not through BMP signaling. CONCLUSIONS:The iron-regulatory serine protease matriptase-2 is expressed in the retina, and absence of this enzyme leads to iron deficiency and increased expression of hemojuvelin and hepcidin in the retina. The upregulation of hepcidin expression in Tmprss6(msk/msk) mouse retinas does not occur via BMP signaling but likely via the proinflammatory cytokine interleukin-6. We conclude that matriptase-2 is a critical participant in retinal iron homeostasis.

Dataset Information

Evidence for the occurrence of membrane-type serine protease 1/matriptase on the basolateral sides of enterocytes.

Publications

Evidence for the occurrence of membrane-type serine protease 1/matriptase on the basolateral sides of enterocytes.

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