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Ghrelin receptors in non-Mammalian vertebrates.

Kaiya H, Kangawa K, Miyazato M - Front Endocrinol (Lausanne) (2013)

Bottom Line: The endogenous ligand, ghrelin, was discovered 3 years later, in 1999, and our understanding of the physiological significance of the ghrelin system in vertebrates has grown steadily since then.Although the ghrelin system in non-mammalian vertebrates is a subject of great interest, protein sequence data for the receptor in non-mammalian vertebrates has been limited until recently, and related biological information has not been well organized.In this review, we summarize current information related to the ghrelin receptor in non-mammalian vertebrates.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, National Cerebral and Cardiovascular Center Research Institute , Osaka , Japan.

ABSTRACT
The growth hormone secretagogue-receptor (GHS-R) was discovered in humans and pigs in 1996. The endogenous ligand, ghrelin, was discovered 3 years later, in 1999, and our understanding of the physiological significance of the ghrelin system in vertebrates has grown steadily since then. Although the ghrelin system in non-mammalian vertebrates is a subject of great interest, protein sequence data for the receptor in non-mammalian vertebrates has been limited until recently, and related biological information has not been well organized. In this review, we summarize current information related to the ghrelin receptor in non-mammalian vertebrates.

No MeSH data available.


Schematic diagram of the second extracellular loop (ECL2) in the GHS-R1a and GHS-R1a-like receptors. Human GHS-R1a, which has a short ECL2 (orange), and tilapia GHS-R1a-like receptor (GHS-R1a-LR), which has a long ECL2 (green), are shown as representative examples. The length of ECL2 in human GHS-R1a is 28 amino acids (AAs), whereas the ECL2 in tilapia GHS-R1a-LR is 43 AAs. Each receptor is classified in a different branch of the phylogenetic tree (Figure 2). GHS-Ra, which includes GHS-R1a or 2a, is found in tetrapods including chickens (birds), mammals, reptiles, and amphibians, as well as some bony fishes such as Coelacanthiformes, Cypriniformes (e.g., goldfish, carp, and zebrafish), and Siluriformes (channel catfish). These animal species have the receptor with the short ECL2. In contrast, GHS-R1a-LR is found only in a fish group that includes Perciformes such as tilapia, Gasterosteiformes such as stickleback and medaka, Tetraodontiformes such as pufferfish, and Salmoniformes such as rainbow trout.
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Figure 4: Schematic diagram of the second extracellular loop (ECL2) in the GHS-R1a and GHS-R1a-like receptors. Human GHS-R1a, which has a short ECL2 (orange), and tilapia GHS-R1a-like receptor (GHS-R1a-LR), which has a long ECL2 (green), are shown as representative examples. The length of ECL2 in human GHS-R1a is 28 amino acids (AAs), whereas the ECL2 in tilapia GHS-R1a-LR is 43 AAs. Each receptor is classified in a different branch of the phylogenetic tree (Figure 2). GHS-Ra, which includes GHS-R1a or 2a, is found in tetrapods including chickens (birds), mammals, reptiles, and amphibians, as well as some bony fishes such as Coelacanthiformes, Cypriniformes (e.g., goldfish, carp, and zebrafish), and Siluriformes (channel catfish). These animal species have the receptor with the short ECL2. In contrast, GHS-R1a-LR is found only in a fish group that includes Perciformes such as tilapia, Gasterosteiformes such as stickleback and medaka, Tetraodontiformes such as pufferfish, and Salmoniformes such as rainbow trout.

Mentions: As shown in Figure 1, there are two isoforms in non-mammalian vertebrates: GHS-Ra and GHS-R1a-LR. GHS-Ra includes GHS-R1a and 2a. Tetrapods including mammals, birds, reptiles, and amphibians have GHS-R1a, whereas some bony fish such as Coelacanthiformes, Cypriniformes (e.g., goldfish, carp, and zebrafish), and Siluriformes (e.g., channel catfish) have both GHS-R1a and 2a. GHS-R1a-LRs show considerable AA identity to GHS-R1a, but have a unique structural feature not found in any tetrapod: the second extracellular loop (ECL2) that connects TMD 4 and 5 is notably longer than that of GHS-R1a (Figure 4). In addition, GHS-R1a-LRs have the characteristic that ghrelin or GHS treatment either does not increase intracellular Ca2+ (23, 26) or requires pharmacological doses to activate the receptor (27, 28). This type of receptor is seen in a limited number of fish classified as Percomorpha within the superorder Acanthopterygii, which is the most evolutionally advanced group of teleosts, including Perciformes such as black porgy and tilapia, Gasterosteiformes such as stickleback and medaka, Tetraodontiformes such as pufferfish, and Salmoniformes such as rainbow trout (Figure 3). An exception is the orange-spotted grouper, which belongs to Perciformes but has an ECL2 that is not long (Figure 3). These species have some morphological characteristics such as a highly mobilized upper jaw, a respiratory tract not linked to the swim bladder, and a splinter article in their fins. Salmoniformes belong to Protacanthopterygii, which contains a number of moderately advanced teleosts. This evolutionary background may be reflected in the molecular evolution and structure of the ghrelin receptor.


Ghrelin receptors in non-Mammalian vertebrates.

Kaiya H, Kangawa K, Miyazato M - Front Endocrinol (Lausanne) (2013)

Schematic diagram of the second extracellular loop (ECL2) in the GHS-R1a and GHS-R1a-like receptors. Human GHS-R1a, which has a short ECL2 (orange), and tilapia GHS-R1a-like receptor (GHS-R1a-LR), which has a long ECL2 (green), are shown as representative examples. The length of ECL2 in human GHS-R1a is 28 amino acids (AAs), whereas the ECL2 in tilapia GHS-R1a-LR is 43 AAs. Each receptor is classified in a different branch of the phylogenetic tree (Figure 2). GHS-Ra, which includes GHS-R1a or 2a, is found in tetrapods including chickens (birds), mammals, reptiles, and amphibians, as well as some bony fishes such as Coelacanthiformes, Cypriniformes (e.g., goldfish, carp, and zebrafish), and Siluriformes (channel catfish). These animal species have the receptor with the short ECL2. In contrast, GHS-R1a-LR is found only in a fish group that includes Perciformes such as tilapia, Gasterosteiformes such as stickleback and medaka, Tetraodontiformes such as pufferfish, and Salmoniformes such as rainbow trout.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
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Figure 4: Schematic diagram of the second extracellular loop (ECL2) in the GHS-R1a and GHS-R1a-like receptors. Human GHS-R1a, which has a short ECL2 (orange), and tilapia GHS-R1a-like receptor (GHS-R1a-LR), which has a long ECL2 (green), are shown as representative examples. The length of ECL2 in human GHS-R1a is 28 amino acids (AAs), whereas the ECL2 in tilapia GHS-R1a-LR is 43 AAs. Each receptor is classified in a different branch of the phylogenetic tree (Figure 2). GHS-Ra, which includes GHS-R1a or 2a, is found in tetrapods including chickens (birds), mammals, reptiles, and amphibians, as well as some bony fishes such as Coelacanthiformes, Cypriniformes (e.g., goldfish, carp, and zebrafish), and Siluriformes (channel catfish). These animal species have the receptor with the short ECL2. In contrast, GHS-R1a-LR is found only in a fish group that includes Perciformes such as tilapia, Gasterosteiformes such as stickleback and medaka, Tetraodontiformes such as pufferfish, and Salmoniformes such as rainbow trout.
Mentions: As shown in Figure 1, there are two isoforms in non-mammalian vertebrates: GHS-Ra and GHS-R1a-LR. GHS-Ra includes GHS-R1a and 2a. Tetrapods including mammals, birds, reptiles, and amphibians have GHS-R1a, whereas some bony fish such as Coelacanthiformes, Cypriniformes (e.g., goldfish, carp, and zebrafish), and Siluriformes (e.g., channel catfish) have both GHS-R1a and 2a. GHS-R1a-LRs show considerable AA identity to GHS-R1a, but have a unique structural feature not found in any tetrapod: the second extracellular loop (ECL2) that connects TMD 4 and 5 is notably longer than that of GHS-R1a (Figure 4). In addition, GHS-R1a-LRs have the characteristic that ghrelin or GHS treatment either does not increase intracellular Ca2+ (23, 26) or requires pharmacological doses to activate the receptor (27, 28). This type of receptor is seen in a limited number of fish classified as Percomorpha within the superorder Acanthopterygii, which is the most evolutionally advanced group of teleosts, including Perciformes such as black porgy and tilapia, Gasterosteiformes such as stickleback and medaka, Tetraodontiformes such as pufferfish, and Salmoniformes such as rainbow trout (Figure 3). An exception is the orange-spotted grouper, which belongs to Perciformes but has an ECL2 that is not long (Figure 3). These species have some morphological characteristics such as a highly mobilized upper jaw, a respiratory tract not linked to the swim bladder, and a splinter article in their fins. Salmoniformes belong to Protacanthopterygii, which contains a number of moderately advanced teleosts. This evolutionary background may be reflected in the molecular evolution and structure of the ghrelin receptor.

Bottom Line: The endogenous ligand, ghrelin, was discovered 3 years later, in 1999, and our understanding of the physiological significance of the ghrelin system in vertebrates has grown steadily since then.Although the ghrelin system in non-mammalian vertebrates is a subject of great interest, protein sequence data for the receptor in non-mammalian vertebrates has been limited until recently, and related biological information has not been well organized.In this review, we summarize current information related to the ghrelin receptor in non-mammalian vertebrates.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, National Cerebral and Cardiovascular Center Research Institute , Osaka , Japan.

ABSTRACT
The growth hormone secretagogue-receptor (GHS-R) was discovered in humans and pigs in 1996. The endogenous ligand, ghrelin, was discovered 3 years later, in 1999, and our understanding of the physiological significance of the ghrelin system in vertebrates has grown steadily since then. Although the ghrelin system in non-mammalian vertebrates is a subject of great interest, protein sequence data for the receptor in non-mammalian vertebrates has been limited until recently, and related biological information has not been well organized. In this review, we summarize current information related to the ghrelin receptor in non-mammalian vertebrates.

No MeSH data available.