| SFTPC | |||||||||||||||||||||||||||||||||||||||||||||||||||
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| Identifiers | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Aliases | SFTPC , BRICD6, PSP-C, SFTP2, SMDP2, SP-C, surfactant protein C, SP5 | ||||||||||||||||||||||||||||||||||||||||||||||||||
| External IDs | OMIM: 178620 MGI: 109517 HomoloGene: 2271 GeneCards: SFTPC | ||||||||||||||||||||||||||||||||||||||||||||||||||
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| Wikidata | |||||||||||||||||||||||||||||||||||||||||||||||||||
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Surfactant protein C (SP-C), is one of the pulmonary surfactant proteins. In humans this is encoded by the SFTPC gene. [5] [6] [7]
It is a membrane protein.
| Surfactant protein C, N terminal propeptide | |||||||||
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 Pig SP-C, corresponds to human mature form | |||||||||
| Identifiers | |||||||||
| Symbol | SP_C-Propep | ||||||||
| Pfam | PF08999 | ||||||||
| InterPro | IPR001729 | ||||||||
| PROSITE | PDOC00298 | ||||||||
| OPM superfamily | 69 | ||||||||
| OPM protein | 1spf | ||||||||
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SFTPC is a 197-residue protein made up of two halves: a unique N-terminal propeptide domain and a C-terminal BRICHOS domain. The around 100-aa long propeptide domain actually contains not only the cleaved part, but also the mature peptide. It can be further broken down into a 23-aa helical transmembrane propeptide proper, the mature secreted SP-C (24-58), and a linker (59-89) that connects to the BRICHOS domain. [8]
The propeptide of pulmonary surfactant C has an N-terminal alpha-helical segment whose suggested function was stabilization of the protein structure, since the mature peptide can irreversibly transform from its native alpha-helical structure to beta-sheet aggregates and form amyloid fibrils. The correct intracellular trafficking of proSP-C has also been reported to depend on the propeptide. [9]
The structure of the BRICHOS domain has been solved. Mutations in this domain also lead to amyloid fibrils made up of the mature peptide, suggesting a chaperone activity. [8]
Mutations are associated with surfactant metabolism dysfunction type 2.
Humans and animals born lacking SP-C tend to develop progressive interstitial lung disease.
Recombinant SP-C is used in Venticute, an artificial lung surfactant.
A process to mass-produce an analogue called rSP-C33Le by fusion with spidroin has been described. [10]
Pulmonary surfactant is a surface-active complex of phospholipids and proteins formed by type II alveolar cells. The proteins and lipids that make up the surfactant have both hydrophilic and hydrophobic regions. By adsorbing to the air-water interface of alveoli, with hydrophilic head groups in the water and the hydrophobic tails facing towards the air, the main lipid component of surfactant, dipalmitoylphosphatidylcholine (DPPC), reduces surface tension.
Aquaporin 1 (AQP-1) is a protein that in humans is encoded by the AQP1 gene.
Collectins (collagen-containing C-type lectins) are a part of the innate immune system. They form a family of collagenous Ca2+-dependent defense lectins, which are found in animals. Collectins are soluble pattern recognition receptors (PRRs). Their function is to bind to oligosaccharide structure or lipids that are on the surface of microorganisms. Like other PRRs they bind pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs) of oligosaccharide origin. Binding of collectins to microorganisms may trigger elimination of microorganisms by aggregation, complement activation, opsonization, activation of phagocytosis, or inhibition of microbial growth. Other functions of collectins are modulation of inflammatory, allergic responses, adaptive immune system and clearance of apoptotic cells.
Surfactant protein D, also known as SP-D, is a lung surfactant protein part of the collagenous family of proteins called collectin. In humans, SP-D is encoded by the SFTPD gene and is part of the innate immune system. Each SP-D subunit is composed of an N-terminal domain, a collagenous region, a nucleating neck region, and a C-terminal lectin domain. Three of these subunits assemble to form a homotrimer, which further assemble into a tetrameric complex.
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.
Surfactant protein B is an essential lipid-associated protein found in pulmonary surfactant. Without it, the lung would not be able to inflate after a deep breath out. It rearranges lipid molecules in the fluid lining the lung so that tiny air sacs in the lung, called alveoli, can more easily inflate.
Deleted in malignant brain tumors 1 protein is a protein that in humans is encoded by the DMBT1 gene.
Multidrug resistance-associated protein 1 (MRP1) is a protein that in humans is encoded by the ABCC1 gene.
Surfactant protein A1(SP-A1), also known as Pulmonary surfactant-associated protein A1(PSP-A) is a protein that in humans is encoded by the SFTPA1 gene.
Probable G-protein coupled receptor 116 is a protein that in humans is encoded by the GPR116 gene. GPR116 has now been shown to play an essential role in the regulation of lung surfactant homeostasis.
NK2 homeobox 1 (NKX2-1), also known as thyroid transcription factor 1 (TTF-1), is a protein which in humans is encoded by the NKX2-1 gene.
Ficolin-1, and also commonly termed M-ficolin is a protein that in humans is encoded by the FCN1 gene.
A disintegrin and metalloproteinase with thrombospondin motifs 8 is an enzyme that in humans is encoded by the ADAMTS8 gene.
Amyloid beta A4 precursor protein-binding family B member 3 is a protein that in humans is encoded by the APBB3 gene.
Ankyrin repeat and sterile alpha motif domain-containing protein 1B is a protein that in humans is encoded by the ANKS1B gene.
Surfactant protein A2(SP-A2), also known as Pulmonary surfactant-associated protein A2(PSP-A2) is a protein that in humans is encoded by the SFTPA2 gene.
A disintegrin and metalloproteinase with thrombospondin motifs 12 is an enzyme that in humans is encoded by the ADAMTS12 gene.
GPR182 is a human gene which is an orphan G-protein coupled receptor.
The BRICHOS family consists of a variety of proteins linked to major diseases, each containing a 100 amino acid BRICHOS domain that is thought to have a chaperone function. These include BRI2, which is related to familial British and Danish dementia ; Chondromodulin-I, related to chondrosarcoma; CA11, related to stomach cancer; and surfactant protein C (SP-C), related to respiratory distress syndrome (RDS).
Surfactant metabolism dysfunction is a condition where pulmonary surfactant is insufficient for adequate respiration. Surface tension at the liquid-air interphase in the alveoli makes the air sacs prone to collapsing post expiration. This is due to the fact that water molecules in the liquid-air surface of alveoli are more attracted to one another than they are to molecules in the air. For sphere-like structures like alveoli, water molecules line the inner walls of the air sacs and stick tightly together through hydrogen bonds. These intermolecular forces put great restraint on the inner walls of the air sac, tighten the surface all together, and unyielding to stretch for inhalation. Thus, without something to alleviate this surface tension, alveoli can collapse and cannot be filled up again. Surfactant is essential mixture that is released into the air-facing surface of inner walls of air sacs to lessen the strength of surface tension. This mixture inserts itself among water molecules and breaks up hydrogen bonds that hold the tension. Multiple lung diseases, like ISD or RDS, in newborns and late-onsets cases have been linked to dysfunction of surfactant metabolism.
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