Limits...
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.

Show MeSH

Related in: MedlinePlus

Theoretical model for the formation of a CatSper hetero-terameric channel. (a) Diagramatic representation of CatSper subunits 1–4. (b) In this model a tetrameric channel is formed via direct interaction of the coiled-coil domains. (c) In this model the channel is brought together via an auxiliary protein or proteins, interaction being mediated via the coiled-coil domains.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC184451&req=5

Figure 10: Theoretical model for the formation of a CatSper hetero-terameric channel. (a) Diagramatic representation of CatSper subunits 1–4. (b) In this model a tetrameric channel is formed via direct interaction of the coiled-coil domains. (c) In this model the channel is brought together via an auxiliary protein or proteins, interaction being mediated via the coiled-coil domains.

Mentions: Additionally, through our bioinformatic analysis of the CatSper family we have annotated coiled-coil domains in all four of the CatSper channels. Alpha helical coiled-coil structural motifs are involved in subunit multimerisation of a large number of proteins. For example, the GABAB receptor assembly is mediated by short (~30 aa) parallel coiled-coil alpha helices in the C-terminal of the GABABR1 and GABABR2 receptors [24]. Coiled-coil domains can also mediate formation of large multi-protein complexes such as the SNARE complex whose core comprises a hetero-tetrameric coiled-coil [25]. Therefore a precedent exists for a four coiled-coil complex. Identification of the coiled-coil domains in the CatSper channels provides an experimentally testable mechanism for CatSper channel tetramerisation. This in theory could involve interaction at the coiled coil domain directly, or via intracellular accessory proteins that interact with the CatSper subunits via the coiled coil motif, anchoring the subunits together. A proposed model for subunit interaction is shown in Figure 10. One question raised by the CatSper1 knockout experiment is how are the channels regulated by cAMP/cGMP? We have searched for cyclic nucleotide binding sites on the CatSper subunits, however no likely domains have been identified, it is therefore possible that this property is conferred by an auxiliary subunit and therefore this would favour the model proposed in Figure 10c.


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)

Theoretical model for the formation of a CatSper hetero-terameric channel. (a) Diagramatic representation of CatSper subunits 1–4. (b) In this model a tetrameric channel is formed via direct interaction of the coiled-coil domains. (c) In this model the channel is brought together via an auxiliary protein or proteins, interaction being mediated via the coiled-coil domains.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC184451&req=5

Figure 10: Theoretical model for the formation of a CatSper hetero-terameric channel. (a) Diagramatic representation of CatSper subunits 1–4. (b) In this model a tetrameric channel is formed via direct interaction of the coiled-coil domains. (c) In this model the channel is brought together via an auxiliary protein or proteins, interaction being mediated via the coiled-coil domains.
Mentions: Additionally, through our bioinformatic analysis of the CatSper family we have annotated coiled-coil domains in all four of the CatSper channels. Alpha helical coiled-coil structural motifs are involved in subunit multimerisation of a large number of proteins. For example, the GABAB receptor assembly is mediated by short (~30 aa) parallel coiled-coil alpha helices in the C-terminal of the GABABR1 and GABABR2 receptors [24]. Coiled-coil domains can also mediate formation of large multi-protein complexes such as the SNARE complex whose core comprises a hetero-tetrameric coiled-coil [25]. Therefore a precedent exists for a four coiled-coil complex. Identification of the coiled-coil domains in the CatSper channels provides an experimentally testable mechanism for CatSper channel tetramerisation. This in theory could involve interaction at the coiled coil domain directly, or via intracellular accessory proteins that interact with the CatSper subunits via the coiled coil motif, anchoring the subunits together. A proposed model for subunit interaction is shown in Figure 10. One question raised by the CatSper1 knockout experiment is how are the channels regulated by cAMP/cGMP? We have searched for cyclic nucleotide binding sites on the CatSper subunits, however no likely domains have been identified, it is therefore possible that this property is conferred by an auxiliary subunit and therefore this would favour the model proposed in Figure 10c.

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