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Novel Cathelicidins from Pigeon Highlights Evolutionary Convergence in Avain Cathelicidins and Functions in Modulation of Innate Immunity.

Yu H, Lu Y, Qiao X, Wei L, Fu T, Cai S, Wang C, Liu X, Zhong S, Wang Y - Sci Rep (2015)

Bottom Line: In macrophages primed by LPS, Cl-CATH2 significantly down-regulated the gene and protein expressions of inducible nitric oxide synthase and pro-inflammatory cytokines while enhancing the anti-inflammatory cytokine, acting through MAPK and NF-κB signaling pathways.Molecular docking shows for the first time that cathelicidin binds to the opening region of LPS-binding pocket on myeloid differentiation factor 2 (MD-2) of toll-like receptor (TLR)4-MD-2 complex, which in turn inhibits the TLR4 pathway.Our results, therefore, provide new insight into the mechanism underlying the blockade of TLR4 signaling by cathelicidins.

View Article: PubMed Central - PubMed

Affiliation: School of Life Science and Biotechnology, Dalian University of Technology, Dalian, Liaoning 116024, China.

ABSTRACT
Cathelicidins are short cationic host defense peptides and play a central role in host innate immune system. Here we identified two novel cathelicidins, Cl-CATH2 and 3, from Columba livia. Evolutionary analysis of avian cathelicidins via phylogenetic tree and Ka/Ks calculations supported the positive selection that prompted evolution of CATH2 to CATH1 and 3, which originate from common ancestor and could belong to one superfamily. Cl-CATH2 and 3 both adopt amphipathic α-helical comformations identified by circular dichroism and the 3D structures built by Rosetta. Cl-CATH2 of CATH2 family with the most expression abundance in bird, exhibited relatively weak antimicrobial activity, but acted instead on the innate immune response without showing undesirable toxicities. In macrophages primed by LPS, Cl-CATH2 significantly down-regulated the gene and protein expressions of inducible nitric oxide synthase and pro-inflammatory cytokines while enhancing the anti-inflammatory cytokine, acting through MAPK and NF-κB signaling pathways. Molecular docking shows for the first time that cathelicidin binds to the opening region of LPS-binding pocket on myeloid differentiation factor 2 (MD-2) of toll-like receptor (TLR)4-MD-2 complex, which in turn inhibits the TLR4 pathway. Our results, therefore, provide new insight into the mechanism underlying the blockade of TLR4 signaling by cathelicidins.

No MeSH data available.


Related in: MedlinePlus

(a) Circular dichroism analysis of Cl-CATH2 in different solvent environments. (b) helix-wheel plots and (c) tertiary structures built by Rosetta ab initio of Cl-CATH2 and Cl-CATH3. For helix-wheel plots, the hydrophobic and hydrophilic residues are separated with dash dot line, with the hydrophilic residues being concentrated on upper side of the helix and hydrophobic ones on the lower. For tertiary structures, intramolecular hydrogen bonds and α-helix are displayed in the ribbon structure. Surface representation of Cl-CATH2 and 3 are shown in blue with positive charges shown in red region.
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f3: (a) Circular dichroism analysis of Cl-CATH2 in different solvent environments. (b) helix-wheel plots and (c) tertiary structures built by Rosetta ab initio of Cl-CATH2 and Cl-CATH3. For helix-wheel plots, the hydrophobic and hydrophilic residues are separated with dash dot line, with the hydrophilic residues being concentrated on upper side of the helix and hydrophobic ones on the lower. For tertiary structures, intramolecular hydrogen bonds and α-helix are displayed in the ribbon structure. Surface representation of Cl-CATH2 and 3 are shown in blue with positive charges shown in red region.

Mentions: The CD spectrum of Cl-CATH2 in the membrane-like environment of 50% TFE/H2O showed one positive band (190 nm) and two negative dichroic bands at 208 and 222 nm, consistent with the α-helical conformations (Fig. 3a). This is concordant with prediction of PSIPRED (v3.3) that generates a 26.47% and 68.97% α-helical component for Cl-CATH2 and 3, respectively. Helical wheel analysis shows that sequences derived from Cl-CATH2 (residues 9–26), Cl-CATH3 (residues 2–19) both form distinct amphipathic structures, and Cl-CATH3 shows more amphipathic than Cl-CATH2 (Fig. 3b), with hydrophilic residues facing upward, while hydrophobic ones facing downward. For Cl-CATH2 and 3, 5 residues (FFIII) and 11 residues (LGAFVVVIWAP) constitute the hydrophobic face, respectively, whereas the other residues comprise the hydrophilic section. Such amphipathic alpha-helix structure is usually adopted by most of small cationic peptides and is thought to be important for their disrupting the membrane integrity3132. The tertiary structures of Cl-CATH2 and 3 built by Rosetta ab initio also demonstrated the components of α-helix and its relative content, highly consistent with the secondary structure predictions (Fig. 3c). Besides, the antiparallel β-strands was also observed juxtaposed the helix in the Cl-CATH2. Cl-CATH3 was also shown to adopt an α-helical structure that contains two antiparallel α-helixes. The positive-charged residues are distributed along the molecular surface to make Cl-CATH2 electrostatic and capable to bind the negative-charged bacterial surface and LPS (Fig. 3c).


Novel Cathelicidins from Pigeon Highlights Evolutionary Convergence in Avain Cathelicidins and Functions in Modulation of Innate Immunity.

Yu H, Lu Y, Qiao X, Wei L, Fu T, Cai S, Wang C, Liu X, Zhong S, Wang Y - Sci Rep (2015)

(a) Circular dichroism analysis of Cl-CATH2 in different solvent environments. (b) helix-wheel plots and (c) tertiary structures built by Rosetta ab initio of Cl-CATH2 and Cl-CATH3. For helix-wheel plots, the hydrophobic and hydrophilic residues are separated with dash dot line, with the hydrophilic residues being concentrated on upper side of the helix and hydrophobic ones on the lower. For tertiary structures, intramolecular hydrogen bonds and α-helix are displayed in the ribbon structure. Surface representation of Cl-CATH2 and 3 are shown in blue with positive charges shown in red region.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4508531&req=5

f3: (a) Circular dichroism analysis of Cl-CATH2 in different solvent environments. (b) helix-wheel plots and (c) tertiary structures built by Rosetta ab initio of Cl-CATH2 and Cl-CATH3. For helix-wheel plots, the hydrophobic and hydrophilic residues are separated with dash dot line, with the hydrophilic residues being concentrated on upper side of the helix and hydrophobic ones on the lower. For tertiary structures, intramolecular hydrogen bonds and α-helix are displayed in the ribbon structure. Surface representation of Cl-CATH2 and 3 are shown in blue with positive charges shown in red region.
Mentions: The CD spectrum of Cl-CATH2 in the membrane-like environment of 50% TFE/H2O showed one positive band (190 nm) and two negative dichroic bands at 208 and 222 nm, consistent with the α-helical conformations (Fig. 3a). This is concordant with prediction of PSIPRED (v3.3) that generates a 26.47% and 68.97% α-helical component for Cl-CATH2 and 3, respectively. Helical wheel analysis shows that sequences derived from Cl-CATH2 (residues 9–26), Cl-CATH3 (residues 2–19) both form distinct amphipathic structures, and Cl-CATH3 shows more amphipathic than Cl-CATH2 (Fig. 3b), with hydrophilic residues facing upward, while hydrophobic ones facing downward. For Cl-CATH2 and 3, 5 residues (FFIII) and 11 residues (LGAFVVVIWAP) constitute the hydrophobic face, respectively, whereas the other residues comprise the hydrophilic section. Such amphipathic alpha-helix structure is usually adopted by most of small cationic peptides and is thought to be important for their disrupting the membrane integrity3132. The tertiary structures of Cl-CATH2 and 3 built by Rosetta ab initio also demonstrated the components of α-helix and its relative content, highly consistent with the secondary structure predictions (Fig. 3c). Besides, the antiparallel β-strands was also observed juxtaposed the helix in the Cl-CATH2. Cl-CATH3 was also shown to adopt an α-helical structure that contains two antiparallel α-helixes. The positive-charged residues are distributed along the molecular surface to make Cl-CATH2 electrostatic and capable to bind the negative-charged bacterial surface and LPS (Fig. 3c).

Bottom Line: In macrophages primed by LPS, Cl-CATH2 significantly down-regulated the gene and protein expressions of inducible nitric oxide synthase and pro-inflammatory cytokines while enhancing the anti-inflammatory cytokine, acting through MAPK and NF-κB signaling pathways.Molecular docking shows for the first time that cathelicidin binds to the opening region of LPS-binding pocket on myeloid differentiation factor 2 (MD-2) of toll-like receptor (TLR)4-MD-2 complex, which in turn inhibits the TLR4 pathway.Our results, therefore, provide new insight into the mechanism underlying the blockade of TLR4 signaling by cathelicidins.

View Article: PubMed Central - PubMed

Affiliation: School of Life Science and Biotechnology, Dalian University of Technology, Dalian, Liaoning 116024, China.

ABSTRACT
Cathelicidins are short cationic host defense peptides and play a central role in host innate immune system. Here we identified two novel cathelicidins, Cl-CATH2 and 3, from Columba livia. Evolutionary analysis of avian cathelicidins via phylogenetic tree and Ka/Ks calculations supported the positive selection that prompted evolution of CATH2 to CATH1 and 3, which originate from common ancestor and could belong to one superfamily. Cl-CATH2 and 3 both adopt amphipathic α-helical comformations identified by circular dichroism and the 3D structures built by Rosetta. Cl-CATH2 of CATH2 family with the most expression abundance in bird, exhibited relatively weak antimicrobial activity, but acted instead on the innate immune response without showing undesirable toxicities. In macrophages primed by LPS, Cl-CATH2 significantly down-regulated the gene and protein expressions of inducible nitric oxide synthase and pro-inflammatory cytokines while enhancing the anti-inflammatory cytokine, acting through MAPK and NF-κB signaling pathways. Molecular docking shows for the first time that cathelicidin binds to the opening region of LPS-binding pocket on myeloid differentiation factor 2 (MD-2) of toll-like receptor (TLR)4-MD-2 complex, which in turn inhibits the TLR4 pathway. Our results, therefore, provide new insight into the mechanism underlying the blockade of TLR4 signaling by cathelicidins.

No MeSH data available.


Related in: MedlinePlus