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Actin‐dependent Pathway is Responsible for Endocytosis of Dipalmitoylphosphatidyl choline (DPPC)‐labeled liposomes by SP‐A deficient mice
Author(s) -
Dodia Chandra,
Fisher Aron B.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1442
Subject(s) - endocytosis , cytochalasin b , cytochalasin d , liposome , cytochalasin , clathrin , chemistry , actin , receptor mediated endocytosis , microbiology and biotechnology , biology , biochemistry , in vitro , receptor , cytoskeleton , cell
Studies with isolated perfused rat lung showed that both clathrin‐mediated and actin‐mediated pathways are responsible for endocytosis of DPPC‐labeled liposomes by granular pneumocytes in the intact lung. (Am. J. Physiol. 284; L981, 2003). Using SP‐A gene targeted mice we studied uptake of 3 H‐DPPC liposomes by isolated mouse lungs under basal and in the presence of 0.1mM 8Br‐cAMP. Unilamellar liposomes [ 3 H‐DPPC: PC: cholesterol: PG, 10:5:3:2, mol fraction] were instilled into the trachea of anesthetized mice and lungs were removed for 2h perfusion. Uptake was calculated as % of instilled dpm in the post‐ lavaged lung. Amantidine, an inhibitor of clathrin‐mediated endocytosis, decreased basal 3 H‐DPPC uptake by 70% in SP‐A +/+ but only 20% in SP‐A −/− (SP‐A +/+ , 5.68 ± 0.1 to 1.68 ± 0.04: SP‐A −/− , 5.75 ± 0.2 to 4.63 ± 0.2). Cytochalasin D, an inhibitor of actin‐dependent endocytosis, decreased uptake by 66% and 61% in SP‐A +/+ and SP‐A −/− , respectively (SP‐A +/+ , 5.68 ± 0.1 to 1.91 ± 0.04: SP‐A −/− , 5.75 ± 0.2 to 2.24 ± 0.2) Similar results were observed in the presence of 8‐Br‐cAMP (SP‐A +/+ , control, 10.54 ± 0.3, amantidine, 3.56 ± 0.07, cytochalasin D, 3.27 ± 0.02; SP‐A −/− control, 5.55 ± 0.1, amantidine, 4.25 ± 0.07, cytochalasin D, 2.16 ± 0.07). As observed previously, 8‐Br‐cAMP stimulated uptake in wild type but not in SP‐A−/− lungs. These data are compatible with a major role for SP‐A in receptor‐mediated endocytosis of DPPC by granular pneumocytes. [HL19737].