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K Rust

Publications and source records attributed to K Rust.

At least 19 recordsLinked to original sources
PubMed2004

Refining the primary open-angle glaucoma GLC1C region on chromosome 3 by haplotype analysis.

The GLC1C locus for primary open-angle glaucoma (POAG) is inherited as an autosomal dominant trait. This region on chromosome 3 is 11 cM long. DNA samples from members of a Greek and an American GLC1C family were obtained to determine whether additional typing of microsatellite markers in family members might narrow the region. GLC1C family members were evaluated clinically for POAG on the basis of open angles, intraocular pressures, cupping of discs, and visual fields. DNA samples from the Greek and Oregon GLC1C families were used to further refine the GLC1C region using microsatellite markers. A total of 22 affected members were identified in the two families. Common alleles for D3S3637 and D3S3612 were present in the disease haplotype from both families, suggesting that they may have a common founder. A newly diagnosed patient in the American family had a recombination in the distal portion of the GLC1C haplotype. This recombination narrows the GLC1C region from 11 to 4 cM.

Chromosome Mapping↗
PubMed2000

Proximal promoter of the surfactant protein D gene: regulatory roles of AP-1, forkhead box, and GT box binding proteins.

Surfactant protein D (SP-D) plays roles in pulmonary host defense and surfactant homeostasis and is increased following lung injury. Because AP-1 proteins regulate cellular responses to diverse environmental stimuli, we hypothesized that the conserved AP-1 motif (at -109) and flanking sequences in the human SP-D promoter contribute to the regulation of SP-D expression. The AP-1 sequence specifically bound to fra-1, junD, and junB in H441 lung adenocarcinoma nuclear extracts. Mutagenesis of the AP-1 motif in a chloramphenicol acetyltransferase reporter construct containing 285 base pairs of upstream sequence nearly abolished promoter activity, and co-transfection of junD significantly increased wild type but not mutant promoter activity. The sequence immediately downstream of the AP-1 element contained a binding site for HNF-3 (FOXA), and simultaneous mutation of this site (fox-d) and an upstream FoxA binding site (-277, fox-u) caused a 4-fold reduction in chloramphenicol acetyltransferase activity. Immediately upstream of the AP-1-binding site, we identified a GT box-containing positive regulatory element. Despite finding regions of limited homology to the thyroid transcription factor 1-binding site, SP-D promoter activity did not require thyroid transcription factor 1. Thus, transcriptional regulation of SP-D gene expression involves complex interactions with ubiquitous and lineage-dependent factors consistent with more generalized roles in innate immunity.

Amino Acid Motifs↗
PubMed1999

GLC1F, a new primary open-angle glaucoma locus, maps to 7q35-q36.

BACKGROUND: A large family with adult-onset primary open-angle glaucoma (POAG) was identified. OBJECTIVE: To initiate a genome-wide scan to map the POAG locus in this family. METHODS: Blood samples or buccal swabs were obtained from 25 members of a large family with POAG after informed consent was obtained. Members and their spouses were evaluated clinically for POAG on the basis of intraocular pressures, cupping of discs, and visual fields. DNA samples were used for a genome-wide screen using microsatellite markers. RESULTS: Ten affected family members in 4 generations showed evidence of POAG including intraocular pressures of 22 mm Hg or more, and/or optic cup-disc ratios of 0.6 or more, and/or visual field defects consistent with glaucomatous damage. Primary open-angle glaucoma segregated as an autosomal dominant trait, with the disease locus mapping to 7q35-q36 between markers D7S2442 and D7S483 with a multipoint lod score of 4.06. CONCLUSION: A sixth gene for POAG (GLC1F) has been mapped to 7q35-q36 in a family with at least 4 generations affected. CLINICAL RELEVANCE: The mapping of this locus further confirms that primary open-angle glaucoma is a heterogeneous group of diseases with at least 6 different loci resulting in a similar phenotype. The eventual ability to classify which major POAG gene an affected person carries could have ramifications for selecting the most effective treatment regimen for that person.

Adult↗
PubMed1998

Age-related macular degeneration. Clinical features in a large family and linkage to chromosome 1q.

OBJECTIVES: To identify the chromosomal location of a disease-causing gene and to describe the clinical characteristics of a large family with age-related macular degeneration (ARMD). METHODS: An ARMD pedigree was identified, and the disease state of family members was documented by stereoscopic fundus photography and was classified using a modified version of the Wisconsin Age-Related Maculopathy Grading System. A genome-wide screen at approximately 6-centimorgan spacing using a DNA-pooling strategy combined with shared-segment analysis was used to identify likely chromosomal regions. The entire family was then screened at each likely locus, and 1 positive locus was refined by screening with markers at an average density of 0.5 centimorgan and subjected to parametric linkage analysis. RESULTS: In the 10 affected family members, ARMD was manifest by the presence of large, soft, confluent drusen accompanied by varying degrees of retinal pigment epithelial degeneration and/or geographic atrophy. Age-related macular degeneration segregated as an autosomal-dominant trait, with the disease locus mapping to chromosome 1q25-q31 between markers D1S466 and D1S413, with a multipoint lod score of 3.00. CONCLUSION: Age-related macular degeneration localized to chromosome 1q25-q31 (gene symbol, ARMD1) as a dominant trait in a large family with a predominantly dry phenotype. CLINICAL RELEVANCE: Identification of ARMD genes will facilitate early diagnosis and aid in understanding the molecular pathophysiological mechanisms of ARMD. This knowledge will contribute to the development of preventive and improved treatment strategies.

Aged↗
PubMed1998

Malattia leventinese: refinement of the genetic locus and phenotypic variability in autosomal dominant macular drusen.

PURPOSE: To study the phenotypic variability in patients inheriting the disease gene for malattia leventinese (dominant macular drusen) and refine the localization of the gene. METHODS: A family with dominant radial drusen was ascertained and studied with clinical examination and DNA linkage analysis. Inheritance of the disease gene was determined by DNA analysis and used to document the variability in phenotypic expression. RESULTS: Fifty family members were studied with fundus photography and genotyping. Linkage analysis showed that the disease in this family was linked to chromosome 2p16-21 with a maximum lod score of 3.72 at D2S2153. An affected patient with obligate recombinations allowed refinement of the disease interval to a 6.2-cM region between D2S2227 and D2S378. The phenotype of older affected patients varied from severe geographic atrophy or subretinal fibrosis to a single druse adjacent to the optic disk. Small and medium-sized, nonradial, and soft macular drusen seen in four older individuals in the family were not specifically associated with the disease haplotype. CONCLUSIONS: Refinement of the localization of the gene for malattia leventinese will facilitate its positional cloning. Genotypic documentation of the variable expression of the disease shows that a single, large, subretinal druse adjacent to the optic disk is consistent with inheritance of the disease gene. Soft macular drusen in low abundance were not specifically associated with inheritance of the disease gene. These results will facilitate the genetic counseling of patients with malattia leventinese. It is unknown what proportion of age-related macular degeneration arises from mutations in disease genes for dominant drusen.

Adolescent↗
PubMed1998

Insulin-like growth factor binding protein-5 expression by human trabecular meshwork.

PURPOSE: The authors found transcript expression for insulin-like growth factor binding protein-5 (IGFBP-5) while screening for uniquely expressed trabecular meshwork (TM) mRNAs. Because the insulin-like growth factor (IGF) autocrine-paracrine system may provide an important signaling mechanism between TM cells and the outflow pathway, the expression of IGFBP-5 and IGF-I receptor in the TM was characterized. METHODS: Poly(A+) RNA was isolated from cell cultures of human TM, ciliary body, retinal pigment epithelium, and skin fibroblasts and subjected to reverse transcription-polymerase chain reaction (RT-PCR) differential display analysis. A unique 980-bp band present in the TM was cloned and sequenced. Additional PCR and Northern analyses were used to define trabecular IGFBP-5 expression. Western immunoblots and confocal immunohistochemistry were used to evaluate the protein expression patterns of IGFBP-5 and the IGF-I receptor. IGF-I and IGF-II were added to trabecular cells in culture, and matrix metalloproteinase production was evaluated. RESULTS: A unique differential display band was identified in the TM. Sequencing of this band identified it as the 3'-untranslated region of IGFBP-5. RT-PCR, using a variety of specific primers for IGFBP-5, Northern analysis, Western immunoblots, and immunohistochemical analysis, confirmed that IGFBP-5 was expressed in the TM. However, IGFBP-5 was also present at low levels in the ciliary body and skin fibroblasts by Northern and Western analysis, in contrast with the differential display findings. In addition, the IGF-I receptor was expressed by the TM and showed cell-surface staining by immunohistochemistry. Trabecular IGFBP-5 was distributed throughout the meshwork in the extracellular matrix and the cells with more staining in the juxtacanalicular region than in the uveal meshwork. IGF-I, but not IGF-II, modestly increased trabecular stromelysin and gelatinase B but not collagenase, gelatinase A, or tissue inhibitor of metalloproteinases 1 or 2. CONCLUSIONS: IGFBP-5 and IGF-I receptor were expressed at significant levels by TM cells and may serve an important role in trabecular function.

Blotting, Northern↗
PubMed1997

Mapping a gene for adult-onset primary open-angle glaucoma to chromosome 3q.

Glaucoma is the third-leading cause of blindness in the world, affecting >13.5 million people. Adult-onset primary open-angle glaucoma (POAG) is the most common form of glaucoma in the United States. We present a family in which adult-onset POAG is inherited as an autosomal dominant trait. Twelve affected family members were identified from 44 at-risk individuals. The disease-causing gene was mapped to chromosome 3q21-24, with analysis of recombinant haplotypes suggesting a total inclusion region of 11.1 cM between markers D3S3637 and D3S1744. This is the first report of mapping of an adult-onset POAG gene to chromosome 3q, gene symbol GLC1C.

Adult↗
PubMed1996

Weill-Marchesani syndrome--possible linkage of the autosomal dominant form to 15q21.1.

Weill-Marchesani syndrome comprises short stature, brachydactyly, microspherophakia, glaucoma, and ectopia lentis is regarded as an autosomal recessive trait (McKusick 277600). We present two families each with affected individuals in 3 generations demonstrating autosomal dominant inheritance of Weill-Marchesani syndrome. Linkage analysis in these 2 families suggests a gene for Weill-Marchesani syndrome maps to 15q21.1. The dislocated lenses and connective tissue disorder in these families suggests that fibrillin-1 and microfibril-associated protein 1, which both map to 15q21.1, are candidate genes for Weill-Marchesani syndrome. Immunohistochemistry staining of skin sections from family 1 showed an apparent decrease in fibrillin staining compared to control individuals.

Abnormalities, Multiple↗
PubMed1996

Biosynthesis of surfactant protein D. Contributions of conserved NH2-terminal cysteine residues and collagen helix formation to assembly and secretion.

Surfactant protein D (SP-D) is preferentially secreted as dodecamers consisting of four collagenous trimers cross-linked by disulfide bonds. In these studies, we examined the biosynthesis of wild-type rat SP-D (RrSP-D) and selected mutants by stably transfected CHO-K1 cells to determine the roles of a conserved N-linked oligosaccharide, the collagen helix, and interchain disulfide bonds in SP-D assembly and secretion. The major intracellular form of RrSP-D accumulated in the RER as complexes containing up to four trimeric subunits. Disulfide cross-link formation and RrSP-D secretion were selectively inhibited by 2,2'-dipyridyl, an inhibitor of prolyl and lysyl hydroxylase, and by 2 mM dithiothreitol, but unaffected by tunicamycin or elimination of the consensus sequence for glycosylation at Asn70. Although mutants with serine substituted for Cys15 and Cys20 (RrSP-Dser15/20) are secreted as trimeric subunits, proteins with single cysteine substitutions were retained in the cell. Surprisingly, the secretion of RrSP-Dser15/20 was unaffected by 2,2'-dipyridyl. These studies strongly suggest that the most important and rate-limiting step for the secretion of SP-D involves the association of cross-linked trimeric subunits to form dodecamers stabilized by specific inter-subunit disulfide cross-links. Interference with collagen helix formation prevents secretion by interfering with efficient disulfide cross-linking of the NH2-terminal domain.

Animals↗
PubMed1996

Site-directed mutagenesis of Cys-15 and Cys-20 of pulmonary surfactant protein D. Expression of a trimeric protein with altered anti-viral properties.

Surfactant protein D (SP-D) molecules are preferentially assembled as dodecamers consisting of trimeric subunits associated at their amino termini. The NH2-terminal sequence of each monomer contains two conserved cysteine residues, which participate in interchain disulfide bonds. In order to study the roles of these residues in SP-D assembly and function, we employed site-directed mutagenesis to substitute serine for cysteine 15 and 20 in recombinant rat SP-D (RrSP-D), and have expressed the mutant (RrSP-Dser15/20) in Chinese hamster ovary (CHO-K1) cells. The mutant, which was efficiently secreted, bound to maltosyl-agarose, but unlike RrSP-D, was assembled exclusively as trimers. The constituent monomers showed a decreased mobility on SDS-polyacrylamide gel electrophoresis resulting from an increase in the size and sialylation of the N-linked oligosaccharide at Asn-70. Although RrSP-Dser15/20 contained a pepsin-resistant triple helical domain, it showed a decreased Tm, and acquired susceptibility to proteolytic degradation. Like RrSP-D, RrSP-Dser15/20 bound to the hemagglutinin of influenza A. However, it showed no viral aggregation and did not enhance the binding of influenza A to neutrophils (PMN), augment PMN respiratory burst, or protect PMNs from deactivation. These studies indicate that amino-terminal disulfides are required to stabilize dodecamers, and support our hypothesis that the oligomerization of trimeric subunits contributes to the anti-microbial properties of SP-D.

Animals↗
PubMed1996

Interactions of recombinant human pulmonary surfactant protein D and SP-D multimers with influenza A.

To further study the structure and function of surfactant protein D (SP-D), recombinant human SP-D (rhSP-D) was isolated from the culture medium of Chinese hamster ovary (CHO)-K1 cells stably transfected with a full-length hSP-D cDNA. Although a significant fraction of the secreted rhSP-D was recovered as dodecamers similar to recombinant rat SP-D (rrSP-D), a major fraction accumulated as multimers of dodecamers indistinguishable from human proteinosis SP-D. As previously shown for the rat protein, rhSP-D agglutinated specific strains of influenza A virus (IAV), inhibited viral hemagglutinin activity, and protected neutrophils (PMN) from deactivation by IAV. However, the potency of rhSP-D multimers was severalfold greater than for purified dodecamers, comparable to natural, proteinosis hSP-D. Although rhSP-D multimers were also more potent than the serum collectins in mediating viral aggregation and protection of PMN, they were less potent than conglutinin in inhibiting infectivity in vitro. These studies establish that the propensity of hSP-D to form multimers of dodecamers is determined by its primary structure and demonstrate carbohydrate recognition domain valency-dependent interactions of SP-D with IAV.

Animals↗
PubMed1996

Characterization of the human surfactant protein D promoter: transcriptional regulation of SP-D gene expression by glucocorticoids.

We have previously described the characterization of genomic clones encoding the entire translated sequence of human pulmonary surfactant protein D (SP-D). We now describe the characterization of a genomic fragment (H5E7) that encodes the entirety of the first translated exon (Exon 2), Intron 1, a short transcribed untranslated sequence (Exon 1; 39 bp), and approximately 4 kb of sequence upstream from the transcription initiation site. The start site was identified by 5'-RACE-PCR cloning and primer extension. A putative TATA box (CATAAATA) was identified approximately 30 bp upstream of the start site. Complete sequencing of a HindIII/SacI fragment (HS-1674) encoding approximately 1.7 kb of sequence 5' to the TATA demonstrated multiple potential cis-regulatory elements including half-site glucocorticoid response elements (GRE), a canonical AP-1 consensus, several AP-1 like sequences, E-box sequences, NF-IL-6 and PEA3 motifs, and putative interferon response elements. H441 lung adenocarcinoma cells, which express low levels of SP-D mRNA, and liver HepG2 cells, were transiently co-transfected with chloramphenicol acetyl transferase (CAT) reporter constructs containing up to 3,000 base pairs of upstream sequence, and with constructs encoding beta-gal. H441 cells transfected with constructs containing at least 161 bp of upstream sequence gave normalized levels of CAT activity greater than or equal to that obtained for parallel positive control transfections using pTK-CAT. Treatment of the cells for 48 h with 50 nM dexamethasone (Dex) gave a 2- to 5-fold increase in CAT activity. Interestingly, a 5'-deletion construct containing 161 bp of upstream sequence (pFS161-CAT) conferred both cell type-restricted and dexamethasone-responsive expression. These studies emphasize the potential complexity of SP-D gene regulation, and further support the hypothesis that the effects of glucocorticoids on SP-D production in vivo are regulated at the level of transcription.

Base Sequence↗
PubMed1994

Recombinant pulmonary surfactant protein D. Post-translational modification and molecular assembly.

Pulmonary surfactant protein D (SP-D) is a member of a family of collagenous C-type lectins that includes the serum mannose binding proteins and surfactant protein A. Recent studies have shown that rat SP-D (rSP-D) molecules are assembled as tetramers of trimeric subunits (12 mers) and that dodecamers can participate in higher orders of molecular assembly involving interactions of the amino-terminal peptide domains. In order to further study the assembly of SP-D in vitro, Chinese hamster ovary K1 cells were transfected with a full-length rat SP-D cDNA, and stable transfectants with high levels of SP-D production (approximately 6 x 10(6) dodecamers/cell/24 h) were obtained using a glutamine synthetase selection system. The secreted molecules (RrSP-D), which were purified by affinity chromatography on maltosyl-agarose, comigrated with rSP-D on SDS-polyacrylamide gel electrophoresis in the presence and absence of reduction, and coeluted with rSP-D dodecamers from 4% agarose. The major bacterial collagenase-resistant peptide showed a decreased mobility on reduction consistent with the formation of intrachain disulfide bonds. A 17-kDa pepsin-resistant fragment was isolated following overnight digestion with pepsin at 27 degrees C, confirming the formation of a triple helical domain comparable in size and thermal stability to that of natural SP-D. The expressed protein contained sialylated endoglycosidase F-sensitive carbohydrate; amino acid analysis of acid and alkaline hydrolysates demonstrated essentially normal levels of hydroxyproline, hydroxylysine, and hydroxylysine-glycosides. Electron microscopic studies showed a molecular structure indistinguishable from lung SP-D, with a similar small subpopulation of molecules showing higher orders of multimerization. Solid-phase neoglycoprotein binding assays gave the same saccharide inhibition profile as natural rat SP-D, and both proteins showed efficient saccharide-dependent agglutination of Escherichia coli. These studies demonstrate that a single genetically distinct chain type can account for the various and complex molecular assemblies of SP-D, and further verify the potential physiologic significance of the disulfide-bonded multimers and higher aggregates isolated from rat, bovine, and human lung lavage.

Agglutination↗
PubMed1993

Genomic organization of human surfactant protein D (SP-D). SP-D is encoded on chromosome 10q22.2-23.1.

Surfactant protein D (SP-D) is a member of the family of mammalian C-type lectins. SP-D is secreted into the pulmonary airspaces by lung epithelial cells and is believed to contribute to the lung's defense against inhaled microorganisms. We have previously characterized cDNAs specific for human SP-D (hSP-D). We now describe the partial characterization of genomic clones for hSP-D and present evidence for an SP-D gene with coding sequences spanning > 11 kilobases on the long arm of chromosome 10. Genomic sequencing demonstrated that the signal peptide/amino-terminal domain, the carbohydrate recognition domain, and the linking sequence between the collagen domain, and carbohydrate recognition domain are each encoded by a single exon, as for surfactant protein A and the mannose-binding protein C. However, sequencing also demonstrated a unique intron-exon structure for the collagen domain which is encoded on five exons, including four tandem exons of 117 bp. The latter exons show marked conservation in the predicted distribution of hydrophilic amino acids, consistent with tandem replication of this collagen gene sequence during evolution. Segregation analysis of HindIII digests of genomic DNA using specific cDNA probes demonstrated selective hybridization of radiolabeled hSP-D cDNA to chromosome 10- and 10q-containing human/hamster somatic hybrids. The presence of SP-D gene sequences was confirmed by DNA amplification using oligomers specific for sequences within the collagen domain of the hSP-D gene. Fluorescence in situ hybridization of metaphase chromosomes using genomic probes gave selective labeling of 10q22.2-23.1. We speculate that SP-D is encoded at a locus on 10q that includes the genes for surfactant protein A.

Amino Acid Sequence↗
PubMed1992

Interactions of surfactant protein D with bacterial lipopolysaccharides. Surfactant protein D is an Escherichia coli-binding protein in bronchoalveolar lavage.

Surfactant protein D (SP-D) is a collagenous glycoprotein that is secreted into the pulmonary airspaces by alveolar type II and nonciliated bronchiolar cells. SP-D exhibits Ca(++)-dependent carbohydrate binding in vitro and is structurally related to the collagenous C-type lectins, including serum conglutinin, serum mannose-binding proteins, and surfactant protein A. Preliminary studies showed calcium- and saccharide-dependent binding of fluorescein-conjugated or radioiodinated SP-D to a variety of microorganisms, including Gram-negative bacteria and fungi. A laboratory strain of Escherichia coli (Y1088) was chosen to further examine the mechanism(s) of binding. Binding of SP-D to Y1088 was time dependent, saturable, and inhibited by cold SP-D or competing saccharides; Scatchard analysis gave a Kd of 2 x 10(-11) M. At higher concentrations, SP-D also caused Ca(++)-dependent agglutination of Y1088 that was inhibited by alpha-glucosyl-containing saccharides, antisera to the carbohydrate-binding domain of SP-D, or Y1088 LPS. Lectin blots showed specific binding of 125I-SP-D to Y1088 LPS, as well as LPS from other several strains of enteric Gram-negative bacteria. Immunogold studies demonstrated strong and uniform surface labeling of the bacteria. Rat and human bronchoalveolar lavage (BAL) caused Ca(++)-dependent agglutination of E. coli that was dose dependent and inhibited by competing saccharides or anti-SP-D. SP-D was selectively and efficiently adsorbed from rat BAL by incubation with E. coli, and incubation of E. coli with radiolabeled rat type II cell medium revealed that SP-D is the major E. coli-binding protein secreted by freshly isolated cells in culture. We suggest that SP-D plays important roles in the lung's defense against Gram-negative bacteria.

Agglutination↗
PubMed1991

Human surfactant protein D: SP-D contains a C-type lectin carbohydrate recognition domain.

Lung surfactant protein D (SP-D) shows calcium-dependent binding to specific saccharides, and is similar in domain structure to certain members of the calcium-dependent (C-type) lectin family. Using a degenerate oligomeric probe corresponding to a conserved peptide sequence derived from the amino-terminus of the putative carbohydrate binding domain of rat and bovine SP-D, we screened a human lung cDNA library and isolated a 1.4-kb cDNA for the human protein. The relationship of the cDNA to SP-D was established by several techniques including amino-terminal microsequencing of SP-D-derived peptides, and immunoprecipitation of translation products of transcribed mRNA with monospecific antibodies to SP-D. In addition, antibodies to a synthetic peptide derived from a predicted unique epitope within the carbohydrate recognition domain of SP-D specifically reacted with SP-D. DNA sequencing demonstrated a noncollagenous carboxy-terminal domain that is highly homologous with the carboxy-terminal globular domain of previously described C-type lectins. This domain contains all of the so-called "invariant residues," including four conserved cysteine residues, and shows high homology with the mannose-binding subfamily of C-type lectins. Sequencing also demonstrated an amino-terminal collagenous domain that contains an uninterrupted sequence of 59 Gly-X-Y triplets and that also contains the only identified consensus for asparagine-linked oligosaccharides. The studies demonstrate that SP-D is a member of the C-type lectin family, and confirm predicted structural similarities to conglutinin, SP-D, and the serum mannose binding proteins.

Amino Acid Sequence↗
PubMed1991

Primary translation products of pulmonary surfactant protein D.

Surfactant protein D (SP-D) is a collagenous, surfactant-associated, carbohydrate-binding protein that is synthesized by alveolar type II epithelial cells. To further characterize SP-D, we isolated RNA from adult rat lungs and rat type II cells and translated mRNAs in vitro. [35S]methionine-labeled translation products were precipitated with antibodies to rat SP-D, resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and visualized by fluorography. Immune precipitates of translation reactions for rat lung or rat type II cells demonstrated a single collagenous polypeptide (39.3 kDa) that was smaller than surfactant-associated SP-D (43 kDa, reduced) but larger than the mature secreted form of rat SP-A. This component was not identified in translation reactions of rat liver, gut, brain, mammary gland, or rat L2 cell RNA. There was a fivefold enrichment of SP-D mRNA in freshly isolated type II cells relative to lung; however, the levels of translatable SP-D mRNA decreased rapidly during the first 24 h of cell culture. The SP-D translation product migrated faster than the major cellular form of SP-D but approximately 1 kDa slower than cellular SP-D synthesized in the presence of 2,2'-dipyridyl plus tunicamycin. Translation in the presence of canine pancreatic microsomes gave a single glycosylated, endoglycosidase F-sensitive form (40.6 kDa) and demonstrated cleavage of a small signal peptide. These results indicate that SP-D is a secretory product of differentiated type II epithelial cells and that SP-D is secreted in a mature form that does not undergo further proteolytic processing in vivo.

Animals↗