Trafficking of newly synthesized surfactant protein B to the lamellar body in alveolar type II cells

2020 ◽  
Vol 381 (3) ◽  
pp. 427-438
Author(s):  
Kazuhiro Osanai ◽  
Shiro Mizuno ◽  
Hirohisa Toga ◽  
Keiji Takahashi
Keyword(s):  
Lamellar Body ◽  
Surfactant Protein ◽  
Alveolar Type ◽  
Type Ii Cells ◽  
Type Ii ◽  
Alveolar Type Ii Cells ◽  
Surfactant Protein B ◽  
Protein B

Binding, uptake, and localization of surfactant protein B in isolated rat alveolar type II cells

1992 ◽  
Vol 262 (6) ◽  
pp. L699-L707 ◽  
Author(s):  
J. S. Breslin ◽  
T. E. Weaver
Keyword(s):  
Surfactant Protein ◽  
Endocytic Pathway ◽  
Alveolar Type ◽  
Type Ii Cells ◽  
Type Ii ◽  
Lamellar Bodies ◽  
Coated Pits ◽  
Alveolar Type Ii Cells ◽  
Surfactant Protein B ◽  
Protein B

This study reports the ability of rat alveolar type II cells to internalize mature bovine surfactant protein B (SP-B) in vitro. Isolated type II cells were incubated with labeled SP-B, and binding and internalization were studied biochemically and morphologically. Biochemical analyses demonstrated a time-dependent association of 125I-labeled SP-B with type II cells; binding steadily increased through 4 h and then remained constant through 20 h of incubation. The association of [3H]SP-B with type II cells was characterized via light and electron microscopic autoradiography. Significant quantities of [3H]SP-B were found at the plasma membrane, in the endocytic pathway, and in lamellar bodies. The pathway of SP-B internalization was not altered by the presence of whole rat surfactant; however, the quantity of SP-B internalized into lamellar bodies was increased. 3[H]SP-B was not associated with coated pits and colocalized with horseradish peroxidase (HRP), consistent with receptor-independent internalization. Cell-associated SP-B was not degraded and was detected in lamellar bodies undergoing exocytosis. These results suggest that SP-B may follow a recycling pathway similar to that previously reported for surfactant phospholipids.

scholarly journals Surfactant Protein B (SP-B) −/− Mice Are Rescued by Restoration of SP-B Expression in Alveolar Type II Cells but Not Clara Cells

1999 ◽  
Vol 274 (27) ◽  
pp. 19168-19174 ◽  
Author(s):  
Sui Lin ◽  
Cheng-Lun Na ◽  
Henry T. Akinbi ◽  
Karen S. Apsley ◽  
Jeffrey A. Whitsett ◽  
...  
Keyword(s):  
Surfactant Protein ◽  
Alveolar Type ◽  
Type Ii Cells ◽  
Type Ii ◽  
Clara Cells ◽  
Alveolar Type Ii Cells ◽  
Surfactant Protein B ◽  
B Mice ◽  
Protein B

Degradation of surfactant protein B by alveolar type II cells

1993 ◽  
Vol 265 (5) ◽  
pp. L448-L455 ◽  
Author(s):  
S. R. Bates ◽  
A. B. Fisher
Keyword(s):  
Degradation Products ◽  
Surfactant Protein ◽  
Alveolar Type ◽  
Type Ii Cells ◽  
Type Ii ◽  
Alveolar Type Ii Cells ◽  
Surfactant Protein B ◽  
The Media ◽  
Lag Period ◽  
Protein B

Surfactant protein B (SP-B) metabolism was studied in primary cultures of alveolar type II cells. Iodinated SP-B reconstituted with surfactant was incorporated rapidly into lung pneumocytes and degraded to trichloroacetic acid (TCA)-soluble products after a lag period of 1 h. Cellular degradation of SP-B occurred whether or not phospholipid liposomes or surfactant was added to the phospholipid-poor SP-B. Uptake and degradation of SP-B at 37 degrees C showed a linear increase up to 3 micrograms SP-B/ml after which the slope of the curve became less steep with increasing concentrations of SP-B in the media. After 4 h of incubation with SP-B, 35% of the SP-B processed was recovered as degradation products. Ninety-six percent of the degradation products were in the media and only 4% were recovered in the cell. The bulk of the breakdown of SP-B occurred inside the type II cells since degradation did not occur at 4 degrees C, showed a 1-h lag period, was proportional to the SP-B protein internalized by the cells, was inhibited 47% by ammonium chloride, was unaffected by the addition of protease inhibitors to the medium, and cell-conditioned medium produced only limited SP-B degradation. Alveolar macrophages also degraded SP-B, whereas other cell types degraded SP-B to a lesser extent. Thus the specificity of the metabolism of SP-B may be through the capability of lung cells to degrade SP-B.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding and uptake of surfactant protein B by alveolar type II cells

1992 ◽  
Vol 263 (3) ◽  
pp. L333-L341 ◽  
Author(s):  
S. R. Bates ◽  
M. F. Beers ◽  
A. B. Fisher
Keyword(s):  
Surfactant Protein ◽  
Alveolar Type ◽  
Type Ii Cells ◽  
Type Ii ◽  
Surface Binding ◽  
Alveolar Type Ii Cells ◽  
Apparent Lack ◽  
High Affinity ◽  
Surfactant Protein B ◽  
Protein B

Surfactant protein B (SP-B, mol wt 9,000, reduced) is a low-molecular-weight hydrophobic protein found in organic extracts of lung surfactant. The interaction of iodinated bovine SP-B (125I-SP-B) and isolated rat alveolar type II cells was examined. The association of SP-B with the lung cells was time and temperature dependent; type II cells exhibited time-dependent binding (at 4 degrees C) and uptake (at 37 degrees C) of SP-B. Binding of phospholipid-poor 125I-SP-B was linearly related to the external SP-B concentration from 0.25 to 60 microgram/ml and was not inhibited by a 60-fold excess of unlabeled SP-B. However, the binding of 125I-SP-B reconstituted with bovine surfactant or with phospholipid-containing liposomes occurred through a high-affinity, saturable process and could be inhibited with unlabeled SP-B. By Scatchard analysis, half-maximum binding in the presence of surfactant occurred at 3.1 +/- 0.7 micrograms SP-B/ml. Saturable binding of SP-B reconstituted with surfactant also occurred with other cell types. The results indicate that SP-B was bound and internalized by type II cells. The apparent lack of specificity in the absence of phospholipid may have been due to the self-association of SP-B. The reconstitution of SP-B with phospholipid altered the binding of phospholipid-poor SP-B from a nonspecific process to a high-affinity process consistent with a cell surface binding site.

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

1993 ◽  
Vol 265 (2) ◽  
pp. L193-L199 ◽  
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)

scholarly journals Transitional human alveolar type II epithelial cells suppress extracellular matrix and growth factor gene expression in lung fibroblasts

2019 ◽  
Vol 317 (2) ◽  
pp. L283-L294 ◽  
Author(s):  
Kelly A. Correll ◽  
Karen E. Edeen ◽  
Rachel L. Zemans ◽  
Elizabeth F. Redente ◽  
Karina A. Serban ◽  
...  
Keyword(s):  
Growth Factor ◽  
Epithelial Cells ◽  
Surfactant Protein ◽  
Lung Fibroblasts ◽  
Alveolar Type ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Alveolar Type Ii Cells ◽  
I Cells

Epithelial-fibroblast interactions are thought to be very important in the adult lung in response to injury, but the specifics of these interactions are not well defined. We developed coculture systems to define the interactions of adult human alveolar epithelial cells with lung fibroblasts. Alveolar type II cells cultured on floating collagen gels reduced the expression of type 1 collagen (COL1A1) and α-smooth muscle actin (ACTA2) in fibroblasts. They also reduced fibroblast expression of hepatocyte growth factor (HGF), fibroblast growth factor 7 (FGF7, KGF), and FGF10. When type II cells were cultured at an air-liquid interface to maintain high levels of surfactant protein expression, this inhibitory activity was lost. When type II cells were cultured on collagen-coated tissue culture wells to reduce surfactant protein expression further and increase the expression of some type I cell markers, the epithelial cells suppressed transforming growth factor-β (TGF-β)-stimulated ACTA2 and connective tissue growth factor (CTGF) expression in lung fibroblasts. Our results suggest that transitional alveolar type II cells and likely type I cells but not fully differentiated type II cells inhibit matrix and growth factor expression in fibroblasts. These cells express markers of both type II cells and type I cells. This is probably a normal homeostatic mechanism to inhibit the fibrotic response in the resolution phase of wound healing. Defining how transitional type II cells convert activated fibroblasts into a quiescent state and inhibit the effects of TGF-β may provide another approach to limiting the development of fibrosis after alveolar injury.

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