CRP‐ductin, the mouse homologue of gp‐340/deleted in malignant brain tumors 1 (DMBT1), binds gram‐positive and gram‐negative bacteria and interacts with lung surfactant protein D
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Media type:
E-Article
Title:
CRP‐ductin, the mouse homologue of gp‐340/deleted in malignant brain tumors 1 (DMBT1), binds gram‐positive and gram‐negative bacteria and interacts with lung surfactant protein D
Description:
<jats:title>Abstract</jats:title><jats:p>CRP‐ductin is a protein expressed mainly by mucosal epithelial cells in the mouse. Sequence homologies indicate that CRP‐ductin is the mouse homologue of human gp‐340, a glycoprotein that agglutinates microorganisms and binds the lung mucosal collectin surfactant protein‐D (SP‐D). Here we report that purified CRP‐ductin binds human SP‐D in a calcium‐dependent manner and that the binding is not inhibited by maltose. The same properties have previously been observed for gp‐340 binding of SP‐D. CRP‐ductin also showed calcium‐dependent binding to both gram‐positive and ‐negative bacteria. A polyclonal antibody raised against gp‐340 reacted specifically with CRP‐ductin in Western blots. Immunoreactivity to CRP‐ductin was found in the exocrine pancreas, in epithelial cells throughout the gastrointestinal tract and in the parotid ducts. A panel of RNA preparations from mouse tissues was screened for CRP‐ductin and SP‐D expression by reverse transcription‐PCR. The pancreas was the main site of synthesis of CRP‐ductin, but transcripts were also readily amplified from salivary gland, the gastrointestinal tract, liver, testis, uterus and lung. Lung was the main site of synthesis of SP‐D, but transcripts were also amplified from uterus, salivary gland, thymus, thyroid gland, pancreas and testis. We conclude that CRP‐ductin is the mouse homologue of human gp‐340 and that its capacity to bind SP‐D as well as gram‐negative and gram‐positive bacteria suggests a role in mucosal immune defense.</jats:p>