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.
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.
Madsen
Jens
J
Department of Immunology and Microbiology, Institute of Medical Biology, University of Southern Denmark, Odense, Denmark.
Tornøe
Ida
I
Nielsen
Ole
O
Lausen
Mette
M
Krebs
Inge
I
Mollenhauer
Jan
J
Kollender
Gaby
G
Poustka
Annemarie
A
Skjødt
Karsten
K
Holmskov
Uffe
U
D000373:Agglutinins; D000818:Animals; D001483:Base Sequence; D002135:Calcium-Binding Proteins; D004268:DNA-Binding Proteins; D005260:Female; D006090:Gram-Negative Bacteria / Q000276:immunology*; D006094:Gram-Positive Bacteria / Q000276:immunology*; D006801:Humans; D018928:Immunity, Mucosal; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D009077:Mucins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D037663:Pulmonary Surfactant-Associated Protein D / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014018:Tissue Distribution; D025521:Tumor Suppressor Proteins
D000373:Agglutinins; D002135:Calcium-Binding Proteins; C108174:DMBT1 protein, human; D004268:DNA-Binding Proteins; C114202:Dmbt1 protein, mouse; D009077:Mucins; D037663:Pulmonary Surfactant-Associated Protein D; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D025521:Tumor Suppressor Proteins