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Glycosylation Effects on FSH-FSHR Interaction Dynamics: A Case Study of Different FSH Glycoforms by Molecular Dynamics Simulations.

Meher BR, Dixit A, Bousfield GR, Lushington GH - PLoS ONE (2015)

Bottom Line: However, substantial qualitative differences emerge between FSH15 and FSH24 when FSH is decorated with a much larger, tetra-antennary glycan.Specifically, the FSHR complex with hypo-glycosylated FSH15 is observed to undergo a significant conformational shift after 5-10 ns of simulation, indicating that FSH15 has greater conformational flexibility than FSH24 which may explain the more favorable FSH15 kinetic profile.FSH15 also exhibits a stronger binding free energy, due in large part to formation of closer and more persistent salt-bridges with FSHR.

View Article: PubMed Central - PubMed

Affiliation: Bioinformatics Core Facility, University of Kansas, Lawrence, Kansas, United States of America.

ABSTRACT
The gonadotropin known as follicle-stimulating hormone (FSH) plays a key role in regulating reproductive processes. Physiologically active FSH is a glycoprotein that can accommodate glycans on up to four asparagine residues, including two sites in the FSHα subunit that are critical for biochemical function, plus two sites in the β subunit, whose differential glycosylation states appear to correspond to physiologically distinct functions. Some degree of FSHβ hypo-glycosylation seems to confer advantages toward reproductive fertility of child-bearing females. In order to identify possible mechanistic underpinnings for this physiological difference we have pursued computationally intensive molecular dynamics simulations on complexes between the high affinity site of the gonadal FSH receptor (FSHR) and several FSH glycoforms including fully-glycosylated (FSH24), hypo-glycosylated (e.g., FSH15), and completely deglycosylated FSH (dgFSH). These simulations suggest that deviations in FSH/FSHR binding profile as a function of glycosylation state are modest when FSH is adorned with only small glycans, such as single N-acetylglucosamine residues. However, substantial qualitative differences emerge between FSH15 and FSH24 when FSH is decorated with a much larger, tetra-antennary glycan. Specifically, the FSHR complex with hypo-glycosylated FSH15 is observed to undergo a significant conformational shift after 5-10 ns of simulation, indicating that FSH15 has greater conformational flexibility than FSH24 which may explain the more favorable FSH15 kinetic profile. FSH15 also exhibits a stronger binding free energy, due in large part to formation of closer and more persistent salt-bridges with FSHR.

No MeSH data available.


(a) Plot showing RMSF values of Cα atoms from MD simulations of dgFSH / FSH24(TAG) (in green), FSH15(TAG) (in black), and FSH24(TAG) (in red). Residues associated with the RMSF, showing each subunit as a bar (α-subunit: yellow bar, β-subunit: green bar and FSHR: light-orange bar) and single-letter code sequences with residue numbers for the regions where RMSF changes reasonably. Residue sequences with reasonable RMSF changes of at least >1.0 Å are labeled inside the bars in each subunit. Ribbon models: Color-coded mapping of the averaged protein flexibility profiles (RMSF values) from MD simulations of the dgFSH, FSH15(TAG) and FSH24(TAG) FSH-FSHR complexes (from left to right). The color-coded sliding scheme is the same as was adopted for Fig 6a. The amino acid sequences for FSHα residues 3–92 (yellow), FSHβ 3–107 (green), and FSHR 1–241 (brown) are shown below. (b) Difference of RMSF values for FSH15(TAG) and FSH24(TAG) from dgFSH. The residues with absolute difference larger than 0.50 Å are labeled by two cutoff dashed black lines.
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pone.0137897.g008: (a) Plot showing RMSF values of Cα atoms from MD simulations of dgFSH / FSH24(TAG) (in green), FSH15(TAG) (in black), and FSH24(TAG) (in red). Residues associated with the RMSF, showing each subunit as a bar (α-subunit: yellow bar, β-subunit: green bar and FSHR: light-orange bar) and single-letter code sequences with residue numbers for the regions where RMSF changes reasonably. Residue sequences with reasonable RMSF changes of at least >1.0 Å are labeled inside the bars in each subunit. Ribbon models: Color-coded mapping of the averaged protein flexibility profiles (RMSF values) from MD simulations of the dgFSH, FSH15(TAG) and FSH24(TAG) FSH-FSHR complexes (from left to right). The color-coded sliding scheme is the same as was adopted for Fig 6a. The amino acid sequences for FSHα residues 3–92 (yellow), FSHβ 3–107 (green), and FSHR 1–241 (brown) are shown below. (b) Difference of RMSF values for FSH15(TAG) and FSH24(TAG) from dgFSH. The residues with absolute difference larger than 0.50 Å are labeled by two cutoff dashed black lines.

Mentions: RMSF for the three FSH glycoforms complexed to the FSHR (dgFSH, FSH15(TAG) and FSH24(TAG)) is shown in Fig 8a. The average RMSF values per-residue for dgFSH, FSH15(TAG) and FSH24(TAG)are 0.85 Å, 0.90 Å and 0.98 Å, respectively. It suggests that global differences in RMSF for these glycoforms are observed, and conformational effects vary as a function of the numbers of TAG bonded to the protein. Moreover, for the FSH-FSHR complex, the average residual atomic fluctuation seems to be higher in case of FSH24(TAG) from dgFSH and FSH15(TAG) with a margin of 0.13 Å and 0.08 Å, respectively. Differences in the RMSF values of the protein for FSH15(TAG) and FSH24(TAG) from dgFSH are shown in Fig 8b. Substantial differences exist for residues: Ser17—Ile23, Val66-Phe72, Lys128—Arg132, Gly248, Asn382, Asp390, Gly394—Ser396, Leu411—Tyr414 and Thr426—Lys432.


Glycosylation Effects on FSH-FSHR Interaction Dynamics: A Case Study of Different FSH Glycoforms by Molecular Dynamics Simulations.

Meher BR, Dixit A, Bousfield GR, Lushington GH - PLoS ONE (2015)

(a) Plot showing RMSF values of Cα atoms from MD simulations of dgFSH / FSH24(TAG) (in green), FSH15(TAG) (in black), and FSH24(TAG) (in red). Residues associated with the RMSF, showing each subunit as a bar (α-subunit: yellow bar, β-subunit: green bar and FSHR: light-orange bar) and single-letter code sequences with residue numbers for the regions where RMSF changes reasonably. Residue sequences with reasonable RMSF changes of at least >1.0 Å are labeled inside the bars in each subunit. Ribbon models: Color-coded mapping of the averaged protein flexibility profiles (RMSF values) from MD simulations of the dgFSH, FSH15(TAG) and FSH24(TAG) FSH-FSHR complexes (from left to right). The color-coded sliding scheme is the same as was adopted for Fig 6a. The amino acid sequences for FSHα residues 3–92 (yellow), FSHβ 3–107 (green), and FSHR 1–241 (brown) are shown below. (b) Difference of RMSF values for FSH15(TAG) and FSH24(TAG) from dgFSH. The residues with absolute difference larger than 0.50 Å are labeled by two cutoff dashed black lines.
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Related In: Results  -  Collection

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pone.0137897.g008: (a) Plot showing RMSF values of Cα atoms from MD simulations of dgFSH / FSH24(TAG) (in green), FSH15(TAG) (in black), and FSH24(TAG) (in red). Residues associated with the RMSF, showing each subunit as a bar (α-subunit: yellow bar, β-subunit: green bar and FSHR: light-orange bar) and single-letter code sequences with residue numbers for the regions where RMSF changes reasonably. Residue sequences with reasonable RMSF changes of at least >1.0 Å are labeled inside the bars in each subunit. Ribbon models: Color-coded mapping of the averaged protein flexibility profiles (RMSF values) from MD simulations of the dgFSH, FSH15(TAG) and FSH24(TAG) FSH-FSHR complexes (from left to right). The color-coded sliding scheme is the same as was adopted for Fig 6a. The amino acid sequences for FSHα residues 3–92 (yellow), FSHβ 3–107 (green), and FSHR 1–241 (brown) are shown below. (b) Difference of RMSF values for FSH15(TAG) and FSH24(TAG) from dgFSH. The residues with absolute difference larger than 0.50 Å are labeled by two cutoff dashed black lines.
Mentions: RMSF for the three FSH glycoforms complexed to the FSHR (dgFSH, FSH15(TAG) and FSH24(TAG)) is shown in Fig 8a. The average RMSF values per-residue for dgFSH, FSH15(TAG) and FSH24(TAG)are 0.85 Å, 0.90 Å and 0.98 Å, respectively. It suggests that global differences in RMSF for these glycoforms are observed, and conformational effects vary as a function of the numbers of TAG bonded to the protein. Moreover, for the FSH-FSHR complex, the average residual atomic fluctuation seems to be higher in case of FSH24(TAG) from dgFSH and FSH15(TAG) with a margin of 0.13 Å and 0.08 Å, respectively. Differences in the RMSF values of the protein for FSH15(TAG) and FSH24(TAG) from dgFSH are shown in Fig 8b. Substantial differences exist for residues: Ser17—Ile23, Val66-Phe72, Lys128—Arg132, Gly248, Asn382, Asp390, Gly394—Ser396, Leu411—Tyr414 and Thr426—Lys432.

Bottom Line: However, substantial qualitative differences emerge between FSH15 and FSH24 when FSH is decorated with a much larger, tetra-antennary glycan.Specifically, the FSHR complex with hypo-glycosylated FSH15 is observed to undergo a significant conformational shift after 5-10 ns of simulation, indicating that FSH15 has greater conformational flexibility than FSH24 which may explain the more favorable FSH15 kinetic profile.FSH15 also exhibits a stronger binding free energy, due in large part to formation of closer and more persistent salt-bridges with FSHR.

View Article: PubMed Central - PubMed

Affiliation: Bioinformatics Core Facility, University of Kansas, Lawrence, Kansas, United States of America.

ABSTRACT
The gonadotropin known as follicle-stimulating hormone (FSH) plays a key role in regulating reproductive processes. Physiologically active FSH is a glycoprotein that can accommodate glycans on up to four asparagine residues, including two sites in the FSHα subunit that are critical for biochemical function, plus two sites in the β subunit, whose differential glycosylation states appear to correspond to physiologically distinct functions. Some degree of FSHβ hypo-glycosylation seems to confer advantages toward reproductive fertility of child-bearing females. In order to identify possible mechanistic underpinnings for this physiological difference we have pursued computationally intensive molecular dynamics simulations on complexes between the high affinity site of the gonadal FSH receptor (FSHR) and several FSH glycoforms including fully-glycosylated (FSH24), hypo-glycosylated (e.g., FSH15), and completely deglycosylated FSH (dgFSH). These simulations suggest that deviations in FSH/FSHR binding profile as a function of glycosylation state are modest when FSH is adorned with only small glycans, such as single N-acetylglucosamine residues. However, substantial qualitative differences emerge between FSH15 and FSH24 when FSH is decorated with a much larger, tetra-antennary glycan. Specifically, the FSHR complex with hypo-glycosylated FSH15 is observed to undergo a significant conformational shift after 5-10 ns of simulation, indicating that FSH15 has greater conformational flexibility than FSH24 which may explain the more favorable FSH15 kinetic profile. FSH15 also exhibits a stronger binding free energy, due in large part to formation of closer and more persistent salt-bridges with FSHR.

No MeSH data available.