Surfactant protein A
{{cs1 config|name-list-style=vanc}}
{{short description|Protein family}}
{{infobox protein
|Name=surfactant, pulmonary-associated protein A1
|caption=
|image=
|width=
|HGNCid=10798
|Symbol=SFTPA1
|AltSymbols=SFTP1
|EntrezGene=6435
|OMIM=178630
|RefSeq=NM_005411
|UniProt=Q8IWL2
|PDB=
|ECnumber=
|Chromosome=10
|Arm=q
|Band=22.3
|LocusSupplementaryData=
}}
{{infobox protein
|Name=surfactant, pulmonary-associated protein A2B
|caption=
|image=
|width=
|HGNCid=10799
|Symbol=SFTPA2B
|AltSymbols=
|EntrezGene=6436
|OMIM=178642
|RefSeq=NM_006926
|UniProt=Q8IWL1
|PDB=
|ECnumber=
|Chromosome=10
|Arm=q
|Band=22.3
|LocusSupplementaryData=
}}
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.{{cite book | vauthors = Boron W, Boulpaep E | title = Medical Physiology | edition = 2nd | location = Philadelphia | publisher = Elsevier | year = 2012 }}
During parturition
The role of surfactant protein A (SP-A) in childbirth is indicated in studies with mice.{{cite journal | vauthors = Condon JC, Jeyasuria P, Faust JM, Mendelson CR | title = Surfactant protein secreted by the maturing mouse fetal lung acts as a hormone that signals the initiation of parturition | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 101 | issue = 14 | pages = 4978–83 | date = April 2004 | pmid = 15044702 | pmc = 387359 | doi = 10.1073/pnas.0401124101 | jstor = 3371804 | bibcode = 2004PNAS..101.4978C | doi-access = free }} 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.{{cite journal | vauthors = 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 | title = Surfactant protein-A as an anti-inflammatory component in the amnion: implications for human pregnancy | journal = Journal of Immunology | volume = 184 | issue = 11 | pages = 6479–91 | date = June 2010 | pmid = 20439915 | pmc = 3103775 | doi = 10.4049/jimmunol.0903867 }} 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,{{cite journal | vauthors = LeVine AM, Bruno MD, Huelsman KM, Ross GF, Whitsett JA, Korfhagen TR | title = Surfactant protein A-deficient mice are susceptible to group B streptococcal infection | journal = Journal of Immunology | volume = 158 | issue = 9 | pages = 4336–40 | date = May 1997 | doi = 10.4049/jimmunol.158.9.4336 | pmid = 9126996 | url = http://www.jimmunol.org/content/158/9/4336 | doi-access = free | url-access = subscription }} Pseudomonas aeruginosa,{{cite journal | vauthors = LeVine AM, Kurak KE, Bruno MD, Stark JM, Whitsett JA, Korfhagen TR | title = Surfactant protein-A-deficient mice are susceptible to Pseudomonas aeruginosa infection | journal = American Journal of Respiratory Cell and Molecular Biology | volume = 19 | issue = 4 | pages = 700–8 | date = October 1998 | pmid = 9761768 | doi = 10.1165/ajrcmb.19.4.3254 }} and likely other organisms. The immune functions of SP-A are time-, temperature-, and concentration-dependent.{{cite journal | vauthors = van Iwaarden F, Welmers B, Verhoef J, Haagsman HP, van Golde LM | title = Pulmonary surfactant protein A enhances the host-defense mechanism of rat alveolar macrophages | journal = American Journal of Respiratory Cell and Molecular Biology | volume = 2 | issue = 1 | pages = 91–8 | date = January 1990 | pmid = 2306370 | doi = 10.1165/ajrcmb/2.1.91 }}
Location
SP-A is found in the pulmonary surfactant in lungs. SP-A and SP-D are also present in extrapulmonary tissues.{{cite journal | vauthors = Haagsman HP, Diemel RV | title = Surfactant-associated proteins: functions and structural variation | journal = Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology | volume = 129 | issue = 1 | pages = 91–108 | date = May 2001 | pmid = 11369536 | doi=10.1016/s1095-6433(01)00308-7}}
See also
External links
- {{MeshName|Surfactant+Protein+A}}