Surfactant protein A

Surfactant protein A is an innate immune system collectin. It is water-soluble and has collagen-like domains similar to SP-D. It is part of the innate immune system and is used to opsonize bacterial cells in the alveoli marking them for phagocytosis by alveolar macrophages. SP-A may also play a role in negative feedback limiting the secretion of pulmonary surfactant. SP-A is not required for pulmonary surfactant to function but does confer immune effects to the organism.[1]

surfactant, pulmonary-associated protein A1
Identifiers
SymbolSFTPA1
Alt. symbolsSFTP1
NCBI gene6435
HGNC10798
OMIM178630
RefSeqNM_005411
UniProtQ8IWL2
Other data
LocusChr. 10 q22.3
surfactant, pulmonary-associated protein A2B
Identifiers
SymbolSFTPA2B
NCBI gene6436
HGNC10799
OMIM178642
RefSeqNM_006926
UniProtQ8IWL1
Other data
LocusChr. 10 q22.3

During parturition

The role of surfactant protein A (SP-A) in childbirth is indicated in studies with mice.[2] Mice which gestate for 19 days typically show signs of SP-A in amniotic fluid at around 16 days. If SP-A is injected into the uterus at 15 days, mice typically deliver early. Inversely, an SP-A inhibitor injection causes notable delays in birth.

The presence of surfactant protein A seemed to trigger an inflammatory response in the uterus of the mice, but later studies found an anti-inflammatory response in humans.[3] In fact, the level of SP-A in a human uterus typically decreases during labor.

Immune functions

Research on SP-A has been done mainly in rodents including mice and rats. This research has shown that mice deficient in SP-A are more susceptible to infections from group B Streptoccoal organisms,[4] Pseudomonas aeruginosa,[5] and likely other organisms. The immune functions of SP-A are time, temperature, and concentration dependant.[6]

Location

SP-A is found in the pulmonary surfactant in lungs. SP-A and SP-D are also present in extrapulmonary tissues.[7]

See also

References
  1. Boron W, Boulpaep E (2012). Medical Physiology (2nd ed.). Philadelphia: Elsevier.
  2. Condon JC, Jeyasuria P, Faust JM, Mendelson CR (April 2004). "Surfactant protein secreted by the maturing mouse fetal lung acts as a hormone that signals the initiation of parturition". Proceedings of the National Academy of Sciences of the United States of America. 101 (14): 4978–83. doi:10.1073/pnas.0401124101. JSTOR 3371804. PMC 387359. PMID 15044702.
  3. Lee DC, Romero R, Kim CJ, Chaiworapongsa T, Tarca AL, Lee J, Suh YL, Mazaki-Tovi S, Vaisbuch E, Mittal P, Draghici S, Erez O, Kusanovic JP, Hassan SS, Kim JS (June 2010). "Surfactant protein-A as an anti-inflammatory component in the amnion: implications for human pregnancy". Journal of Immunology. 184 (11): 6479–91. doi:10.4049/jimmunol.0903867. PMC 3103775. PMID 20439915.
  4. LeVine AM, Bruno MD, Huelsman KM, Ross GF, Whitsett JA, Korfhagen TR (May 1997). "Surfactant protein A-deficient mice are susceptible to group B streptococcal infection". Journal of Immunology. 158 (9): 4336–40. PMID 9126996.
  5. LeVine AM, Kurak KE, Bruno MD, Stark JM, Whitsett JA, Korfhagen TR (October 1998). "Surfactant protein-A-deficient mice are susceptible to Pseudomonas aeruginosa infection". American Journal of Respiratory Cell and Molecular Biology. 19 (4): 700–8. doi:10.1165/ajrcmb.19.4.3254. PMID 9761768.
  6. van Iwaarden F, Welmers B, Verhoef J, Haagsman HP, van Golde LM (January 1990). "Pulmonary surfactant protein A enhances the host-defense mechanism of rat alveolar macrophages". American Journal of Respiratory Cell and Molecular Biology. 2 (1): 91–8. doi:10.1165/ajrcmb/2.1.91. PMID 2306370.
  7. Haagsman HP, Diemel RV (May 2001). "Surfactant-associated proteins: functions and structural variation". Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology. 129 (1): 91–108. doi:10.1016/s1095-6433(01)00308-7. PMID 11369536.


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