Limits...
APH1 polar transmembrane residues regulate the assembly and activity of presenilin complexes.

Pardossi-Piquard R, Yang SP, Kanemoto S, Gu Y, Chen F, Böhm C, Sevalle J, Li T, Wong PC, Checler F, Schmitt-Ulms G, St George-Hyslop P, Fraser PE - J. Biol. Chem. (2009)

Bottom Line: Substitution of charged (E84A, R87A) or polar (Q83A) residues in TM3 had no effect on complex assembly or activity.Substitution with a negatively charged side chain (His-to-Asp) or altering the structural location of the histidines also disrupted gamma-secretase binding and abolished functionality of APH1.These results suggest that the conserved transmembrane histidine residues contribute to APH1 function and can affect presenilin catalytic activity.

View Article: PubMed Central - PubMed

Affiliation: Centre for Research in Neurodegenerative Diseases, Toronto, Ontario M5S 3H2, Canada.

ABSTRACT
Complexes involved in the gamma/epsilon-secretase-regulated intramembranous proteolysis of substrates such as the amyloid-beta precursor protein are composed primarily of presenilin (PS1 or PS2), nicastrin, anterior pharynx defective-1 (APH1), and PEN2. The presenilin aspartyl residues form the catalytic site, and similar potentially functional polar transmembrane residues in APH1 have been identified. Substitution of charged (E84A, R87A) or polar (Q83A) residues in TM3 had no effect on complex assembly or activity. In contrast, changes to either of two highly conserved histidines (H171A, H197A) located in TM5 and TM6 negatively affected PS1 cleavage and altered binding to other secretase components, resulting in decreased amyloid generating activity. Charge replacement with His-to-Lys substitutions rescued nicastrin maturation and PS1 endoproteolysis leading to assembly of the formation of structurally normal but proteolytically inactive gamma-secretase complexes. Substitution with a negatively charged side chain (His-to-Asp) or altering the structural location of the histidines also disrupted gamma-secretase binding and abolished functionality of APH1. These results suggest that the conserved transmembrane histidine residues contribute to APH1 function and can affect presenilin catalytic activity.

Show MeSH

Related in: MedlinePlus

Identification of conserved polar residues in APH1 transmembrane domains. A, positively charged residues (His-171, His-197, and Arg-87), a negatively charged residue (Glu-84), and an uncharged polar residue (Gln-83) are highly conserved within species from human, chicken, Xenopus, Drosophila to C. elegans. B, TM topology of APH1, APP-CTF, and PS1 showing the location of the conserved polar/charged residues within the membrane. The polar/charged residues on APH1 are located at about the same distance from the cytoplasm as the proposed catalytic aspartate residues of PS1 (Asp-257 and Asp-385) relative to the γ- and ϵ-cleavage sites within the APP-CTF.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2713549&req=5

Figure 1: Identification of conserved polar residues in APH1 transmembrane domains. A, positively charged residues (His-171, His-197, and Arg-87), a negatively charged residue (Glu-84), and an uncharged polar residue (Gln-83) are highly conserved within species from human, chicken, Xenopus, Drosophila to C. elegans. B, TM topology of APH1, APP-CTF, and PS1 showing the location of the conserved polar/charged residues within the membrane. The polar/charged residues on APH1 are located at about the same distance from the cytoplasm as the proposed catalytic aspartate residues of PS1 (Asp-257 and Asp-385) relative to the γ- and ϵ-cleavage sites within the APP-CTF.

Mentions: Inspection of the primary sequence and membrane topology of APH1 revealed several highly conserved polar or potentially charged residues within the selected transmembrane domains. Because of their hydrophilic properties, these particular amino acids are not as commonly found in membrane environments and may, therefore, be of functional significance. More specifically, residues identified are the negatively charged Asp-84, positively charged Arg-87, and polar Gln-83 located in TM3 and His-171 in TM5 and His-197 in TM6, both of which have imidazole side chains that can be positively charged under physiological conditions (Fig. 1A). All of these transmembrane residues are conserved across a broad range of species from human to Drosophila and Caenorhabditis elegans and may be involved, for example, in protein-protein binding through electrostatic interactions or hydrogen bonding. Such interactions could be important for the intramolecular association of APH1 transmembrane (TM) domains to promote structural stability or could mediate interactions with other γ-secretase components. Alternatively, these membrane-embedded residues may contribute to functional aspects of APH1 as they relate to presenilin-mediated proteolysis.


APH1 polar transmembrane residues regulate the assembly and activity of presenilin complexes.

Pardossi-Piquard R, Yang SP, Kanemoto S, Gu Y, Chen F, Böhm C, Sevalle J, Li T, Wong PC, Checler F, Schmitt-Ulms G, St George-Hyslop P, Fraser PE - J. Biol. Chem. (2009)

Identification of conserved polar residues in APH1 transmembrane domains. A, positively charged residues (His-171, His-197, and Arg-87), a negatively charged residue (Glu-84), and an uncharged polar residue (Gln-83) are highly conserved within species from human, chicken, Xenopus, Drosophila to C. elegans. B, TM topology of APH1, APP-CTF, and PS1 showing the location of the conserved polar/charged residues within the membrane. The polar/charged residues on APH1 are located at about the same distance from the cytoplasm as the proposed catalytic aspartate residues of PS1 (Asp-257 and Asp-385) relative to the γ- and ϵ-cleavage sites within the APP-CTF.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2713549&req=5

Figure 1: Identification of conserved polar residues in APH1 transmembrane domains. A, positively charged residues (His-171, His-197, and Arg-87), a negatively charged residue (Glu-84), and an uncharged polar residue (Gln-83) are highly conserved within species from human, chicken, Xenopus, Drosophila to C. elegans. B, TM topology of APH1, APP-CTF, and PS1 showing the location of the conserved polar/charged residues within the membrane. The polar/charged residues on APH1 are located at about the same distance from the cytoplasm as the proposed catalytic aspartate residues of PS1 (Asp-257 and Asp-385) relative to the γ- and ϵ-cleavage sites within the APP-CTF.
Mentions: Inspection of the primary sequence and membrane topology of APH1 revealed several highly conserved polar or potentially charged residues within the selected transmembrane domains. Because of their hydrophilic properties, these particular amino acids are not as commonly found in membrane environments and may, therefore, be of functional significance. More specifically, residues identified are the negatively charged Asp-84, positively charged Arg-87, and polar Gln-83 located in TM3 and His-171 in TM5 and His-197 in TM6, both of which have imidazole side chains that can be positively charged under physiological conditions (Fig. 1A). All of these transmembrane residues are conserved across a broad range of species from human to Drosophila and Caenorhabditis elegans and may be involved, for example, in protein-protein binding through electrostatic interactions or hydrogen bonding. Such interactions could be important for the intramolecular association of APH1 transmembrane (TM) domains to promote structural stability or could mediate interactions with other γ-secretase components. Alternatively, these membrane-embedded residues may contribute to functional aspects of APH1 as they relate to presenilin-mediated proteolysis.

Bottom Line: Substitution of charged (E84A, R87A) or polar (Q83A) residues in TM3 had no effect on complex assembly or activity.Substitution with a negatively charged side chain (His-to-Asp) or altering the structural location of the histidines also disrupted gamma-secretase binding and abolished functionality of APH1.These results suggest that the conserved transmembrane histidine residues contribute to APH1 function and can affect presenilin catalytic activity.

View Article: PubMed Central - PubMed

Affiliation: Centre for Research in Neurodegenerative Diseases, Toronto, Ontario M5S 3H2, Canada.

ABSTRACT
Complexes involved in the gamma/epsilon-secretase-regulated intramembranous proteolysis of substrates such as the amyloid-beta precursor protein are composed primarily of presenilin (PS1 or PS2), nicastrin, anterior pharynx defective-1 (APH1), and PEN2. The presenilin aspartyl residues form the catalytic site, and similar potentially functional polar transmembrane residues in APH1 have been identified. Substitution of charged (E84A, R87A) or polar (Q83A) residues in TM3 had no effect on complex assembly or activity. In contrast, changes to either of two highly conserved histidines (H171A, H197A) located in TM5 and TM6 negatively affected PS1 cleavage and altered binding to other secretase components, resulting in decreased amyloid generating activity. Charge replacement with His-to-Lys substitutions rescued nicastrin maturation and PS1 endoproteolysis leading to assembly of the formation of structurally normal but proteolytically inactive gamma-secretase complexes. Substitution with a negatively charged side chain (His-to-Asp) or altering the structural location of the histidines also disrupted gamma-secretase binding and abolished functionality of APH1. These results suggest that the conserved transmembrane histidine residues contribute to APH1 function and can affect presenilin catalytic activity.

Show MeSH
Related in: MedlinePlus