Uptake of pulmonary surfactant protein C into adult rat lung lamellar bodies

Previous studies have provided evidence that a large proportion of secreted surfactant lipids is taken up from the alveolar air space by type II cells, incorporated into lamellar bodies, and resecreted. Our goal was to characterize the clearance of exogenously administered recombinant surfactant protein C (SP-C) and to determine if SP-C is taken up by type II cells and incorporated into lamellar bodies. SP-C was radiolabeled by alkylation with [3H]iodoacetic acid and retained its ability to enhance phospholipid adsorption to an air-liquid interface. A mixture of 100 micrograms phospholipid radiolabeled with [14C]dipalmitoylphosphatidylcholine and 10 micrograms SP-C was instilled into the lungs of spontaneously breathing anesthetized adult rats. At later times, the lungs were lavaged and subcellular organelles were isolated. The radioactivity of both phospholipids and SP-C (expressed as disintegrations per minute per microgram phospholipid) in lamellar body fractions increased up to 4 h postinstillation and began to decline after approximately 4 h. The results of this study suggest that SP-C and dipalmitoylphosphatidylcholine are taken up promptly from the alveolar air space and are incorporated into lamellar bodies with time courses that do not differ greatly.

Download Full-text

Posttranslational processing of surfactant protein C in rat type II cells

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1995.269.6.l727 ◽

1995 ◽

Vol 269 (6) ◽

pp. L727-L733 ◽

Cited By ~ 19

Author(s):

D. K. Vorbroker ◽

W. F. Voorhout ◽

T. E. Weaver ◽

J. A. Whitsett

Keyword(s):

Protein C ◽

Surfactant Protein ◽

Proteolytic Processing ◽

Proteinase K ◽

Multivesicular Bodies ◽

Type Ii Cells ◽

Type Ii ◽

Lamellar Bodies ◽

Surfactant Protein C

Pulmonary surfactant consists of phospholipids and proteins that form a stable monolayer at the surface of the alveoli to prevent lung collapse. Surfactant protein C (SP-C) is a hydrophobic 4-kDa palmitoylated protein derived from a 21-kDa precursor. We determined the membrane insertion, proteolytic processing, and subcellular location of 21-kDa proSP-C. In vitro, proSP-C associated with canine microsomes, and the NH2-terminal of proSP-C was protected from digestion with proteinase K, suggesting that proSP-C was inserted in a type III transmembrane configuration. Treatment of freshly isolated rat type II cells with cerulenin blocked acylation of the 21-kDa precursor. Pulse-chase labeling of type II cells demonstrated proSP-C processing intermediates of 19, 16, and 13 kDa that contained the NH2-terminal of proSP-C. Proteolytic processing of proSP-C was inhibited by incubation at 20 degrees C, suggesting that processing of proSP-C begins in a late Golgi or post-Golgi compartment. Immunogold labeling of rat lung with an antiserum to the NH2-terminal of proSP-C identified proSP-C in the trans-Golgi and multivesicular bodies but not in lamellar bodies. These findings suggest that proSP-C processing takes place in the trans-Golgi and multivesicular bodies before SP-C is incorporated into lamellar bodies.

Download Full-text

Pulmonary surfactant protein A-mediated uptake of phosphatidylcholine by alveolar type II cells

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1993.265.2.l193 ◽

1993 ◽

Vol 265 (2) ◽

pp. L193-L199 ◽

Cited By ~ 12

Author(s):

A. Tsuzuki ◽

Y. Kuroki ◽

T. Akino

Keyword(s):

Pulmonary Surfactant ◽

Protein A ◽

Lamellar Body ◽

Surfactant Protein ◽

Surfactant Protein A ◽

Alveolar Type ◽

Type Ii Cells ◽

Type Ii ◽

Lamellar Bodies ◽

Pulmonary Surfactant Protein

Pulmonary surfactant protein A (SP-A)-mediated uptake of phosphatidylcholine (PC) by alveolar type II cells was investigated. SP-A enhanced the uptake of liposomes containing dipalmitoylphosphatidylcholine (DPPC), 1-palmitoyl-2-linoleoyl phosphatidylcholine (PLPC), or 1,2-dihexadecyl-sn-glycero-3-phosphocholine (DPPC-ether), a diether analogue of DPPC, but about twice as much DPPC was taken up by type II cells as PLPC or DPPC-ether. When subcellular distribution was analyzed, 51.3 +/- 2.9% (mean +/- SD, n = 3) of cell-associated radiolabeled DPPC was recovered in the lamellar body-rich fraction in the presence of SP-A, whereas only 19.3 +/- 1.9% (mean +/- SD, n = 3) was found to this fraction in the absence of SP-A. When type II cells were incubated either with DPPC at 0 degree C or with DPPC-ether at 37 degrees C, or no cells were included, low proportions of the cell-associated lipids were present in the fractions corresponding to lamellar bodies even in the presence of SP-A. Anti-SP-A antibody significantly reduced the radioactivity incorporated into the lamellar body fraction. Phosphatidylcholine that had been incorporated into lamellar bodies remained largely intact when SP-A was present. Subcellular fractionations of type II cells with radiolabeled SP-A and DPPC revealed that the sedimentation characteristics of cell-associated SP-A are different from those of DPPC, although a small broad peak of radiolabeled SP-A was found in the lamellar body fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Download Full-text

Histone deacetylase inhibitor restores surfactant protein-C expression in alveolar-epithelial type II cells and attenuates bleomycin-induced pulmonary fibrosisin vivo

Experimental Lung Research ◽

10.3109/01902148.2015.1060275 ◽

2015 ◽

Vol 41 (8) ◽

pp. 422-434 ◽

Cited By ~ 23

Author(s):

Chiharu Ota ◽

Mitsuhiro Yamada ◽

Naoya Fujino ◽

Hozumi Motohashi ◽

Yukiko Tando ◽

...

Keyword(s):

Histone Deacetylase ◽

Histone Deacetylase Inhibitor ◽

Protein C ◽

Surfactant Protein ◽

Type Ii Cells ◽

Type Ii ◽

Surfactant Protein C ◽

Alveolar Epithelial ◽

Deacetylase Inhibitor

Download Full-text

Autophagy regulates hyperoxia-induced intracellular accumulation of surfactant protein C in alveolar type II cells

Molecular and Cellular Biochemistry ◽

10.1007/s11010-015-2494-z ◽

2015 ◽

Vol 408 (1-2) ◽

pp. 181-189 ◽

Cited By ~ 9

Author(s):

Liang Zhang ◽

Shuang Zhao ◽

Li-Jie Yuan ◽

Hong-Min Wu ◽

Hong Jiang ◽

...

Keyword(s):

Protein C ◽

Surfactant Protein ◽

Alveolar Type ◽

Type Ii Cells ◽

Type Ii ◽

Intracellular Accumulation ◽

Alveolar Type Ii Cells ◽

Surfactant Protein C

Download Full-text

Endocytosed SP-A and surfactant lipids are sorted to different organelles in rat type II pneumocytes

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.2001.281.2.l345 ◽

2001 ◽

Vol 281 (2) ◽

pp. L345-L360 ◽

Cited By ~ 24

Author(s):

Heide Wissel ◽

Andrea Lehfeldt ◽

Petra Klein ◽

Torsten Müller ◽

Paul A. Stevens

Keyword(s):

Cell Surface ◽

Intracellular Transport ◽

Protein A ◽

Lamellar Body ◽

Surfactant Protein ◽

Type Ii Cells ◽

Type Ii ◽

Lamellar Bodies ◽

Type Ii Pneumocytes ◽

Early Endosomes

Intracellular transport of endocytosed surfactant protein A (SP-A) and lipid was investigated in isolated rat type II cells. After internalization, SP-A and lipid are taken up via the coated-pit pathway and reside in a common compartment, positive for the early endosomal marker EEA1 but negative for the lamellar body marker 3C9. SP-A then recycles rapidly to the cell surface via Rab4-associated recycling vesicles. Internalized lipid is transported toward a Rab7-, CD63-, 3C9-positive compartment, i.e., lamellar bodies. Inhibition of calmodulin led to inhibition of uptake and transport out of the EEA1-positive endosome and thus of resecretion of both components. Inhibition of intravesicular acidification (bafilomycin A1) led to decreased uptake of both surfactant components. It inhibited transport out of early endosomes for lipid only, not for SP-A. We conclude that in type II cells, endocytosed SP-A and lipid are transported toward a common early endosomal compartment. Thereafter, both components dissociate. SP-A is rapidly recycled to the cell surface and does not enter classic lamellar bodies. Lipid is transported toward lamellar bodies.

Download Full-text

Synthesis and processing of hydrophobic surfactant protein C by isolated rat type II cells

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1995.269.6.l744 ◽

1995 ◽

Vol 269 (6) ◽

pp. L744-L753 ◽

Cited By ~ 13

Author(s):

M. F. Beers ◽

C. Lomax

Keyword(s):

Protein C ◽

Brefeldin A ◽

Surfactant Protein ◽

Alveolar Type ◽

Type Ii Cells ◽

Metabolic Labeling ◽

Type Ii ◽

Surfactant Protein C ◽

Adult Rat ◽

The Media

Surfactant protein C (SP-C) is a 3.7-kDa hydrophobic peptide isolated from organic extracts of pulmonary surfactant which is secreted by alveolar type II cells after synthesis and posttranslational processing of a 21-kDa proSP-C peptide (SP-C21). Previously characterized epitope-specific proSP-C antisera were used to study early proteolytic steps of proSP-C processing by adult rat type II cells. Western blotting and immunocytochemistry using anti-NPROSP-C (epitope = Met10-Glu23) each demonstrated marked attenuation of proSP-C protein expression by culture on plastic. Processing was therefore studied by metabolic labeling of freshly isolated type II cells maintained in suspension in serum-free media. With the use of anti-NPROSP-C, immunoprecipitation of cell lysates continuously labeled for 4 h with [35S]methionine demonstrated radiolabeled bands of M(r) 21, 16, and 10-6,000 while anti-CTERMSP-C (epitope = Ser149-Ser166) failed to detect 35S-bands of M(r) < 16,000. Pulse-chase studies demonstrated synthesis of 35S-proSP-C21 with a time-dependent dependent appearance of 16-kDa and 10- to 6-kDa forms which was blocked by addition of brefeldin A. SP-C precursors were not detected in the media. Quantitative analysis of the major bands by direct beta-counting indicated a precursor-product relationship between SP-C21 and SP-C16. These results demonstrate the utility of freshly isolated type II cells for characterization of SP-C synthetic pathways and show that early proSP-C processing events include synthesis of a 21-kDa primary translation product followed by extensive intracellular proteolysis of the proSP-C COOH-terminal in subcellular compartments of type II cells which are distal to the trans-Golgi network.

Download Full-text

Partial SP-B deficiency perturbs lung function and causes air space abnormalities

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00392.2004 ◽

2005 ◽

Vol 288 (6) ◽

pp. L1154-L1161 ◽

Cited By ~ 21

Author(s):

Lori L. Nesslein ◽

Kristin R. Melton ◽

Machiko Ikegami ◽

Cheng-Lun Na ◽

Susan E. Wert ◽

...

Keyword(s):

Cell Sorting ◽

Lamellar Body ◽

Surfactant Protein ◽

Cellular Heterogeneity ◽

Type Ii Cells ◽

Type Ii ◽

Surfactant Protein B ◽

Air Space ◽

Partial Deficiency ◽

Deficient Mice

Surfactant protein B (SP-B) is required for function of newborn and adult lung, and partial deficiency has been associated with susceptibility to lung injury. In the present study, transgenic mice were produced in which expression of SP-B in type II epithelial cells was conditionally regulated. Concentrations of SP-B were maintained at 60–70% of that normally present in control. Immunostaining for SP-B demonstrated cellular heterogeneity in expression of the protein. In subsets of type II cells in which SP-B staining was decreased, immunostaining for pro-SP-C was increased and lamellar body ultrastructure was disrupted, consistent with focal SP-B deficiency. Fluorescence-activated cell sorting analyses of freshly isolated type II cells identified a population of cells with low SP-B content and a smaller population with increased SP-B content, confirming nonuniform expression of the SP-B transgene. Focal air space enlargement, without cellular infiltration or inflammation, was observed. Pressure-volume curves indicated that maximal tidal volume was unchanged; however, hysteresis was modestly altered and residual volumes were significantly decreased in the SP-B-deficient mice. Chronic, nonuniform SP-B deficiency perturbed pulmonary function and caused air space enlargement.

Download Full-text

Surfactant protein C in fetal and ventilated preterm rabbit lungs

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1999.277.6.l1104 ◽

1999 ◽

Vol 277 (6) ◽

pp. L1104-L1108 ◽

Cited By ~ 14

Author(s):

Gary F. Ross ◽

Machiko Ikegami ◽

Wolfram Steinhilber ◽

Alan H. Jobe

Keyword(s):

Protein C ◽

Surfactant Protein ◽

Type Ii Cells ◽

Mrna Levels ◽

Type Ii ◽

Surfactant Protein C ◽

Mature Type ◽

Alveolar Surfactant ◽

Surfactant Lipid ◽

Molar Percent

The developing lung contains surfactant protein (SP) C mRNA levels comparable to term values before mature type II cells and alveolar surfactant lipids are detectable. Estimates of the amount of mature SP-C in the alveolar lavages of preterm lungs are not available. We used an antibody to a recombinant human SP-C to measure the amount of SP-C in alveolar lavages of preterm fetal rabbits, ventilated preterm rabbits, and term rabbits. The amounts of SP-C were compared with the amounts of saturated phosphatidylcholine (Sat PC). Median Sat PC amounts increased about 680-fold, and median SP-C values increased by over 5,000-fold in alveolar washes from 27 days gestation to term. There was no increase in Sat PC or SP-C with ventilation at 27 and 28 days gestation, but ventilation increased both Sat PC and SP-C at 29 days gestation. The molar percent of SP-C relative to Sat PC also increased with gestational age and with ventilation at 29 days gestation. proSP-C was abundant in a membrane fraction from lung tissue at 27 and 28 days gestation when minimal mature SP-C was detected in alveolar washes. At 29 days and at term, proSP-C decreased in membrane fractions. The preterm lung that is surfactant lipid deficient is also severely deficient in mature SP-C.

Download Full-text