Pollen grains bind to lung alveolar type II cells (A549) via lung surfactant protein A (SP-A).
Lung surfactant protein A (SP-A) is the most abundant surfactant-associated protein present in the lung. A receptor for SP-A has been shown to be present on A549 alveolar type II cells and on other cell types, including alveolar macrophage. The SP-A receptor on A549 cells has been identified as the collection receptor, or C1q receptor, which binds several structurally-related ligands. SP-A contains C-type lectin domains, but the role of carbohydrate binding by SP-A in physiological and pathological phenomena is not yet established. In this paper we report the binding of SP-A to pollen from Populus nigra italica (Lombardy Poplar), Poa pratensis (Kentucky blue grass), Secale cerale (cultivated rye) and Ambrosia elatior (short ragweed). Saturable and concentration dependent binding of SP-A to pollen grains was observed. Interaction of SP-A with pollen grains takes place through water-extractable components, in which the major species present, in Lombardy polar pollen, are 57 kD and 7 kD (glyco)proteins. The binding of SP-A to pollen grains and their aqueous extracts was calcium ion dependent and was inhibited by mannose, and is therefore mediated by the lectin domain. Binding of SP-A to pollen grains was found to mediate adhesion of pollen grains to A549 cells. The results suggest that pollen grains or other carbohydrate-bearing particles (e.g. microorganisms) could potentially interact with different cell types via the collection receptor (C1q Receptor) in the presence of SP-A.
Malhotra
R
R
Department of Biochemistry, University of Oxford, UK.
Haurum
J
J
Thiel
S
S
Jensenius
J C
JC
Sim
R B
RB
D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D006801:Humans; D016676:Macrophages, Alveolar / Q000378:metabolism*; D011058:Pollen / Q000378:metabolism*; D011485:Protein Binding; D011510:Proteolipids / Q000378:metabolism*; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000378:metabolism*
D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D002118:Calcium