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Infection and Immunity, March 2007, p. 1403-1412, Vol. 75, No. 3
0019-9567/07/$08.00+0     doi:10.1128/IAI.01341-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Surfactant Protein A2 (SP-A2) Variants Expressed in CHO Cells Stimulate Phagocytosis of Pseudomonas aeruginosa More than Do SP-A1 Variants{triangledown}

Anatoly N. Mikerov,1 Guirong Wang,1 Todd M. Umstead,2 Mario Zacharatos,1 Neal J. Thomas,2,4 David S. Phelps,2 and Joanna Floros1,2,3*

Departments of Cellular and Molecular Physiology,1 Pediatrics,2 Obstetrics and Gynecology,3 Health Evaluation Sciences, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania 170334

Received 21 August 2006/ Returned for modification 19 October 2006/ Accepted 21 December 2006

Surfactant protein A (SP-A) enhances phagocytosis of Pseudomonas aeruginosa. Two functional genes, SP-A1 and SP-A2, encode human SP-A. As we showed before, baculovirus-mediated insect cell-expressed SP-A2 enhances the association of P. aeruginosa with rat alveolar macrophages (rAMs) more than does SP-A1. However, true phagocytosis (internalization) was not shown, and insect cell derived proteins lack or are defective in certain mammalian posttranslational modifications that may be important for SP-A1 and SP-A2 activity and specificity. Here we used SP-A1 (6A2, 6A4) and SP-A2 (1A0, 1A1) allele variants expressed by CHO (Chinese hamster ovary) mammalian cells to study their effect on association and/or internalization of P. aeruginosa by rAMs and/or human AMs (hAMs) and to study if phagocytosis can be modulated differentially and/or more effectively by CHO cell-expressed SP-A variants than by insect-cell expressed SP-A variants. For cell association and internalization assessments, light microscopy and fluorescence-activated cell sorter analyses were used, respectively. We found the following for the first time. (i) SP-A2 variants enhanced phagocytosis (cell association and/or internalization) of P. aeruginosa more than SP-A1 variants did, and the cell association correlated with internalization. (ii) Differences in the activities of SP-A variants were observed in the following order: 1A1>1A0>6A2>6A4. (iii) rAMs, although more active than hAMs, are an appropriate model, as SP-A2 variants exhibited activity higher than that seen for SP-A1 variants with either rAMs or hAMs. (iv) CHO cell-expressed SP-A was considerably more active than insect cell-expressed variants. We conclude that SP-A2 variants stimulate phagocytosis of P. aeruginosa more effectively than SP-A1 variants and that posttranslational modifications positively influence the phagocytic activity of SP-A.

* Corresponding author. Mailing address: Department of Cellular and Molecular Physiology, H166, The Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033. Phone: (717) 531-6972. Fax: (717) 531-7667. E-mail: jfloros{at}psu.edu.

{triangledown} Published ahead of print on 12 January 2007.

Editor: J. B. Bliska

Infection and Immunity, March 2007, p. 1403-1412, Vol. 75, No. 3
0019-9567/07/$08.00+0     doi:10.1128/IAI.01341-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Bruce, S. R., Atkins, C. L., Colasurdo, G. N., Alcorn, J. L. (2009). Respiratory syncytial virus infection alters surfactant protein A expression in human pulmonary epithelial cells by reducing translation efficiency. Am. J. Physiol. Lung Cell. Mol. Physiol. 297: L559-L567 [Abstract] [Full Text]  
  • Wang, G., Guo, X., Silveyra, P., Kimball, S. R., Floros, J. (2009). Cap-independent translation of human SP-A 5'-UTR variants: a double-loop structure and cis-element contribution. Am. J. Physiol. Lung Cell. Mol. Physiol. 296: L635-L647 [Abstract] [Full Text]  
  • Mikerov, A. N., Umstead, T. M., Gan, X., Huang, W., Guo, X., Wang, G., Phelps, D. S., Floros, J. (2008). Impact of ozone exposure on the phagocytic activity of human surfactant protein A (SP-A) and SP-A variants. Am. J. Physiol. Lung Cell. Mol. Physiol. 294: L121-L130 [Abstract] [Full Text]  


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