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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.


Related in: MedlinePlus

FSH/FSHR quaternary and primary structures examined in this study.(a). Structure showing the FSH-FSHR complex with the partial glycosylation of NAG (N-acetylglucosamine). Ribbons colored green and cyan identify FSHα and FSHβ subunits, respectively. The former is glycosylated by NAG at sequence positions 52 and 78, while the latter is glycosylated at positions 7 and 24. NAGs are shown as grey colored stick models. The pink ribbon shows a portion of the FSH receptor extracellular domain that possesses the high affinity FSH binding site. (b). The amino acid sequences for FSHα residues 3–92 (yellow), FSHβ 3–107 (green), and FSHR 1–241 (brown) are shown below. In subsequent figures a colored bar will indicate each protein, as the software numbers the residues 1–437.
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pone.0137897.g001: FSH/FSHR quaternary and primary structures examined in this study.(a). Structure showing the FSH-FSHR complex with the partial glycosylation of NAG (N-acetylglucosamine). Ribbons colored green and cyan identify FSHα and FSHβ subunits, respectively. The former is glycosylated by NAG at sequence positions 52 and 78, while the latter is glycosylated at positions 7 and 24. NAGs are shown as grey colored stick models. The pink ribbon shows a portion of the FSH receptor extracellular domain that possesses the high affinity FSH binding site. (b). The amino acid sequences for FSHα residues 3–92 (yellow), FSHβ 3–107 (green), and FSHR 1–241 (brown) are shown below. In subsequent figures a colored bar will indicate each protein, as the software numbers the residues 1–437.

Mentions: One particular cellular interaction, whose function and efficacy is known to depend on glycosylation state, is the association of follicle-stimulating hormone (FSH) with its cellular receptor (FSHR). FSH is a gonadotropic hormone responsible for hormonal signaling in the gonads. Heterodimeric in form, FSH shares a highly homologous 92–96 amino acid residue alpha subunit with other glycoprotein hormones, such as luteinizing hormone (LH), thyroid-stimulating hormone (TSH) and chorionic gonadotropin (CG). Each of these hormones exhibits a distinct biochemical function courtesy of their individual beta subunits and from their distinct glycosylation profiles. In the case of FSH, the heterodimer can experience glycosylation at as many as four distinct asparagine residues: FSHα sequence positions 52 and 78 and FSHβ positions 7 and 24. Fig 1 shows the topology and relative orientation of glycosylated FSH in complex with its receptor, FSHR. The critical role of FSH glycosylation state in fostering FSHR activation has been known for some time [4–6], but the more recent discovery of variations in the glycosylation state of human FSHβ, for which hypo-glycosylated variants have been identified [7,8] has fostered a hypothesis that the different isoforms produce key differences in reproductive function [9], and in particular contribute to a decline in female fertility as a function of advancing age [9]. Since fertility treatments have arisen that involve FSHR stimulation via urinary or recombinant FSH preparations (e.g., [10]), it has become particularly important to characterize the dependence of fertility on specific glycosylation states in order to potentially optimize the conditions for fertilization. Another health issue whose phenotypic characterization may also relate to FSH glycosylation state is post-menopausal acceleration of osteoporosis [11].


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)

FSH/FSHR quaternary and primary structures examined in this study.(a). Structure showing the FSH-FSHR complex with the partial glycosylation of NAG (N-acetylglucosamine). Ribbons colored green and cyan identify FSHα and FSHβ subunits, respectively. The former is glycosylated by NAG at sequence positions 52 and 78, while the latter is glycosylated at positions 7 and 24. NAGs are shown as grey colored stick models. The pink ribbon shows a portion of the FSH receptor extracellular domain that possesses the high affinity FSH binding site. (b). The amino acid sequences for FSHα residues 3–92 (yellow), FSHβ 3–107 (green), and FSHR 1–241 (brown) are shown below. In subsequent figures a colored bar will indicate each protein, as the software numbers the residues 1–437.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4581761&req=5

pone.0137897.g001: FSH/FSHR quaternary and primary structures examined in this study.(a). Structure showing the FSH-FSHR complex with the partial glycosylation of NAG (N-acetylglucosamine). Ribbons colored green and cyan identify FSHα and FSHβ subunits, respectively. The former is glycosylated by NAG at sequence positions 52 and 78, while the latter is glycosylated at positions 7 and 24. NAGs are shown as grey colored stick models. The pink ribbon shows a portion of the FSH receptor extracellular domain that possesses the high affinity FSH binding site. (b). The amino acid sequences for FSHα residues 3–92 (yellow), FSHβ 3–107 (green), and FSHR 1–241 (brown) are shown below. In subsequent figures a colored bar will indicate each protein, as the software numbers the residues 1–437.
Mentions: One particular cellular interaction, whose function and efficacy is known to depend on glycosylation state, is the association of follicle-stimulating hormone (FSH) with its cellular receptor (FSHR). FSH is a gonadotropic hormone responsible for hormonal signaling in the gonads. Heterodimeric in form, FSH shares a highly homologous 92–96 amino acid residue alpha subunit with other glycoprotein hormones, such as luteinizing hormone (LH), thyroid-stimulating hormone (TSH) and chorionic gonadotropin (CG). Each of these hormones exhibits a distinct biochemical function courtesy of their individual beta subunits and from their distinct glycosylation profiles. In the case of FSH, the heterodimer can experience glycosylation at as many as four distinct asparagine residues: FSHα sequence positions 52 and 78 and FSHβ positions 7 and 24. Fig 1 shows the topology and relative orientation of glycosylated FSH in complex with its receptor, FSHR. The critical role of FSH glycosylation state in fostering FSHR activation has been known for some time [4–6], but the more recent discovery of variations in the glycosylation state of human FSHβ, for which hypo-glycosylated variants have been identified [7,8] has fostered a hypothesis that the different isoforms produce key differences in reproductive function [9], and in particular contribute to a decline in female fertility as a function of advancing age [9]. Since fertility treatments have arisen that involve FSHR stimulation via urinary or recombinant FSH preparations (e.g., [10]), it has become particularly important to characterize the dependence of fertility on specific glycosylation states in order to potentially optimize the conditions for fertilization. Another health issue whose phenotypic characterization may also relate to FSH glycosylation state is post-menopausal acceleration of osteoporosis [11].

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.


Related in: MedlinePlus