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Identification of human and mouse CatSper3 and CatSper4 genes: characterisation of a common interaction domain and evidence for expression in testis.

Lobley A, Pierron V, Reynolds L, Allen L, Michalovich D - Reprod. Biol. Endocrinol. (2003)

Bottom Line: However, neither CatSper1 or CatSper2 have been shown to function as cation channels when transfected into cells, singly or in conjunction.Furthermore, all four of the CatSper proteins are predicted to contain a common coiled-coil protein-protein interaction domain in their C-terminal tail.Coupled with expression data this leads to the hypothesis that the CatSper proteins form a functional hetero-tetrameric channel in sperm.

View Article: PubMed Central - HTML - PubMed

Affiliation: Target Discovery, Inpharmatica Ltd, 60 Charlotte Street, London W1T 2NU, UK. a.lobley@inpharmatica.co.uk

ABSTRACT

Background: CatSper1 and CatSper2 are two recently identified channel-like proteins, which show sperm specific expression patterns. Through targeted mutagenesis in the mouse, CatSper1 has been shown to be required for fertility, sperm motility and for cAMP induced Ca2+ current in sperm. Both channels resemble a single pore forming repeat from a four repeat voltage dependent Ca2+ /Na+ channel. However, neither CatSper1 or CatSper2 have been shown to function as cation channels when transfected into cells, singly or in conjunction. As the pore forming units of voltage gated cation channels form a tetramer it has been suggested that the known CatSper proteins require additional subunits and/or interaction partners to function.

Results: Using in silico gene identification and prediction techniques, we have identified two further members of the CatSper family, CatSper3 and Catsper4. Each carries a single channel-forming domain with the predicted pore-loop containing the consensus sequence TxDxW. Each of the new CatSper genes has evidence for expression in the testis. Furthermore we identified coiled-coil protein-protein interaction domains in the C-terminal tails of each of the CatSper channels, implying that CatSper channels 1,2,3 and 4 may interact directly or indirectly to form a functional tetramer.

Conclusions: The topological and sequence relationship of CatSper1 and CatSper2 to the four repeat Ca2+ /Na+ channels suggested other members of this family may exist. We have identified a further two novel CatSper genes, conserved in both the human and mouse genomes. Furthermore, all four of the CatSper proteins are predicted to contain a common coiled-coil protein-protein interaction domain in their C-terminal tail. Coupled with expression data this leads to the hypothesis that the CatSper proteins form a functional hetero-tetrameric channel in sperm.

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Alignment of Human CatSper voltage sensor and pore forming regions with selected L- and T-type calcium channels. (a) Voltage sensor region of CatSper human protein sequences aligned with repeats 1–4 of selected human L- and T-type calcium channels; CCAA_Human – calcium channel alpha1A (SWISSPROT O00555), CCAS_Human – calcium channel 1S (SWISSPROT Q13698) and CCAH_Human – calcium channel 1H (SWISSPROT O95180). (b) Pore selectivity region of CatSper ion channel family aligned with selected human L- and T-type calcium channels ion transport repeats.
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Figure 6: Alignment of Human CatSper voltage sensor and pore forming regions with selected L- and T-type calcium channels. (a) Voltage sensor region of CatSper human protein sequences aligned with repeats 1–4 of selected human L- and T-type calcium channels; CCAA_Human – calcium channel alpha1A (SWISSPROT O00555), CCAS_Human – calcium channel 1S (SWISSPROT Q13698) and CCAH_Human – calcium channel 1H (SWISSPROT O95180). (b) Pore selectivity region of CatSper ion channel family aligned with selected human L- and T-type calcium channels ion transport repeats.

Mentions: The voltage sensor lies within S4 transmembrane helix and is involved in channel activation via positively charged residues positioned every 3–4 amino acids [21]. Sequence alignment of S4 helices of selected voltage gated Ca2+ channels with CatSper family (Figure 6a) shows that a pattern of regular repeating basic residues (arginine/lysine) are also present in the CatSper1 and CatSper2 S4 helices. However, in CatSper3 and CatSper4 subunits the repeating charged residues are conserved to a lesser extent with only two of the four charged residues found, suggesting a reduced voltage dependent mechanism of activation [21].


Identification of human and mouse CatSper3 and CatSper4 genes: characterisation of a common interaction domain and evidence for expression in testis.

Lobley A, Pierron V, Reynolds L, Allen L, Michalovich D - Reprod. Biol. Endocrinol. (2003)

Alignment of Human CatSper voltage sensor and pore forming regions with selected L- and T-type calcium channels. (a) Voltage sensor region of CatSper human protein sequences aligned with repeats 1–4 of selected human L- and T-type calcium channels; CCAA_Human – calcium channel alpha1A (SWISSPROT O00555), CCAS_Human – calcium channel 1S (SWISSPROT Q13698) and CCAH_Human – calcium channel 1H (SWISSPROT O95180). (b) Pore selectivity region of CatSper ion channel family aligned with selected human L- and T-type calcium channels ion transport repeats.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC184451&req=5

Figure 6: Alignment of Human CatSper voltage sensor and pore forming regions with selected L- and T-type calcium channels. (a) Voltage sensor region of CatSper human protein sequences aligned with repeats 1–4 of selected human L- and T-type calcium channels; CCAA_Human – calcium channel alpha1A (SWISSPROT O00555), CCAS_Human – calcium channel 1S (SWISSPROT Q13698) and CCAH_Human – calcium channel 1H (SWISSPROT O95180). (b) Pore selectivity region of CatSper ion channel family aligned with selected human L- and T-type calcium channels ion transport repeats.
Mentions: The voltage sensor lies within S4 transmembrane helix and is involved in channel activation via positively charged residues positioned every 3–4 amino acids [21]. Sequence alignment of S4 helices of selected voltage gated Ca2+ channels with CatSper family (Figure 6a) shows that a pattern of regular repeating basic residues (arginine/lysine) are also present in the CatSper1 and CatSper2 S4 helices. However, in CatSper3 and CatSper4 subunits the repeating charged residues are conserved to a lesser extent with only two of the four charged residues found, suggesting a reduced voltage dependent mechanism of activation [21].

Bottom Line: However, neither CatSper1 or CatSper2 have been shown to function as cation channels when transfected into cells, singly or in conjunction.Furthermore, all four of the CatSper proteins are predicted to contain a common coiled-coil protein-protein interaction domain in their C-terminal tail.Coupled with expression data this leads to the hypothesis that the CatSper proteins form a functional hetero-tetrameric channel in sperm.

View Article: PubMed Central - HTML - PubMed

Affiliation: Target Discovery, Inpharmatica Ltd, 60 Charlotte Street, London W1T 2NU, UK. a.lobley@inpharmatica.co.uk

ABSTRACT

Background: CatSper1 and CatSper2 are two recently identified channel-like proteins, which show sperm specific expression patterns. Through targeted mutagenesis in the mouse, CatSper1 has been shown to be required for fertility, sperm motility and for cAMP induced Ca2+ current in sperm. Both channels resemble a single pore forming repeat from a four repeat voltage dependent Ca2+ /Na+ channel. However, neither CatSper1 or CatSper2 have been shown to function as cation channels when transfected into cells, singly or in conjunction. As the pore forming units of voltage gated cation channels form a tetramer it has been suggested that the known CatSper proteins require additional subunits and/or interaction partners to function.

Results: Using in silico gene identification and prediction techniques, we have identified two further members of the CatSper family, CatSper3 and Catsper4. Each carries a single channel-forming domain with the predicted pore-loop containing the consensus sequence TxDxW. Each of the new CatSper genes has evidence for expression in the testis. Furthermore we identified coiled-coil protein-protein interaction domains in the C-terminal tails of each of the CatSper channels, implying that CatSper channels 1,2,3 and 4 may interact directly or indirectly to form a functional tetramer.

Conclusions: The topological and sequence relationship of CatSper1 and CatSper2 to the four repeat Ca2+ /Na+ channels suggested other members of this family may exist. We have identified a further two novel CatSper genes, conserved in both the human and mouse genomes. Furthermore, all four of the CatSper proteins are predicted to contain a common coiled-coil protein-protein interaction domain in their C-terminal tail. Coupled with expression data this leads to the hypothesis that the CatSper proteins form a functional hetero-tetrameric channel in sperm.

Show MeSH
Related in: MedlinePlus