Limits...
Intramolecular immunological signal hypothesis revived--structural background of signalling revealed by using Congo Red as a specific tool.

Jagusiak A, Konieczny L, Krol M, Marszalek P, Piekarska B, Piwowar P, Roterman I, Rybarska J, Stopa B, Zemanek G - Mini Rev Med Chem (2015)

Bottom Line: As a result, even low-affinity transiently binding antibodies can participate in immune complexes in the presence of Congo red, although immune complexes formed by these antibodies fail to trigger the complement cascade.This indicates that binding of antibodies to the antigen may not, by itself, fulfill the necessary conditions to generate the signal which triggers effector activity.These findings, together with the results of molecular dynamics simulation studies, enable us to conclude that, apart from the necessary assembling of antibodies, intramolecular structural changes generated by strains which associate high- affinity bivalent antibody fitting to antigen determinants are also required to cross the complement activation threshold.

View Article: PubMed Central - PubMed

Affiliation: .

ABSTRACT
Micellar structures formed by self-assembling Congo red molecules bind to proteins penetrating into function-related unstable packing areas. Here, we have used Congo red--a supramolecular protein ligand--to investigate how the intramolecular structural changes that take place in antibodies following antigen binding lead to complement activation. According to our findings, Congo red binding significantly enhances the formation of antigen-antibody complexes. As a result, even low-affinity transiently binding antibodies can participate in immune complexes in the presence of Congo red, although immune complexes formed by these antibodies fail to trigger the complement cascade. This indicates that binding of antibodies to the antigen may not, by itself, fulfill the necessary conditions to generate the signal which triggers effector activity. These findings, together with the results of molecular dynamics simulation studies, enable us to conclude that, apart from the necessary assembling of antibodies, intramolecular structural changes generated by strains which associate high- affinity bivalent antibody fitting to antigen determinants are also required to cross the complement activation threshold.

Show MeSH
MD simulation [63] approach to analyzing the signal generation mechanism. MD simulation results presenting the movement of Fabdomains and revealing structural relaxation which results from asymmetric intervention in the L chain, disconnected in the elbow region.Lines connecting Ala75-Gly124-Gln202 in the H chain and Ser92- Leu107-Thr210 in the L chain denote domain position prior to (thin)and following (thick) removal of the L chain. Structural changes are depicted as XZ (A), YZ (B) and XY (C) projections. D – Ribbon-likepresentation of superimposed Fab molecules to visualize the displacement of C domains.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4440395&req=5

Figure 8: MD simulation [63] approach to analyzing the signal generation mechanism. MD simulation results presenting the movement of Fabdomains and revealing structural relaxation which results from asymmetric intervention in the L chain, disconnected in the elbow region.Lines connecting Ala75-Gly124-Gln202 in the H chain and Ser92- Leu107-Thr210 in the L chain denote domain position prior to (thin)and following (thick) removal of the L chain. Structural changes are depicted as XZ (A), YZ (B) and XY (C) projections. D – Ribbon-likepresentation of superimposed Fab molecules to visualize the displacement of C domains.

Mentions: Asymmetry of the Fab fragment, caused by variations in the stability of V domains (H and L) in the polyclonal population and by their variable involvement in antigen binding, leads us to expect a similar variability in strain generation [49-57]. While in our model structural modifications focus on the light chain – likely due to the limited stability of its V domain and (usually) lower engagement in antigen complexation – the heavy chain remains the deciding factor in enabling relaxed-state rotational movements, producing favorable conditions for C1q complexation. MD simulations were used to verify that this mechanism is possible in practice. Relaxation was obtained using a Fab fragment with the L chain disconnected in the elbow region (L107, N108) (Fig. 8).


Intramolecular immunological signal hypothesis revived--structural background of signalling revealed by using Congo Red as a specific tool.

Jagusiak A, Konieczny L, Krol M, Marszalek P, Piekarska B, Piwowar P, Roterman I, Rybarska J, Stopa B, Zemanek G - Mini Rev Med Chem (2015)

MD simulation [63] approach to analyzing the signal generation mechanism. MD simulation results presenting the movement of Fabdomains and revealing structural relaxation which results from asymmetric intervention in the L chain, disconnected in the elbow region.Lines connecting Ala75-Gly124-Gln202 in the H chain and Ser92- Leu107-Thr210 in the L chain denote domain position prior to (thin)and following (thick) removal of the L chain. Structural changes are depicted as XZ (A), YZ (B) and XY (C) projections. D – Ribbon-likepresentation of superimposed Fab molecules to visualize the displacement of C domains.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4440395&req=5

Figure 8: MD simulation [63] approach to analyzing the signal generation mechanism. MD simulation results presenting the movement of Fabdomains and revealing structural relaxation which results from asymmetric intervention in the L chain, disconnected in the elbow region.Lines connecting Ala75-Gly124-Gln202 in the H chain and Ser92- Leu107-Thr210 in the L chain denote domain position prior to (thin)and following (thick) removal of the L chain. Structural changes are depicted as XZ (A), YZ (B) and XY (C) projections. D – Ribbon-likepresentation of superimposed Fab molecules to visualize the displacement of C domains.
Mentions: Asymmetry of the Fab fragment, caused by variations in the stability of V domains (H and L) in the polyclonal population and by their variable involvement in antigen binding, leads us to expect a similar variability in strain generation [49-57]. While in our model structural modifications focus on the light chain – likely due to the limited stability of its V domain and (usually) lower engagement in antigen complexation – the heavy chain remains the deciding factor in enabling relaxed-state rotational movements, producing favorable conditions for C1q complexation. MD simulations were used to verify that this mechanism is possible in practice. Relaxation was obtained using a Fab fragment with the L chain disconnected in the elbow region (L107, N108) (Fig. 8).

Bottom Line: As a result, even low-affinity transiently binding antibodies can participate in immune complexes in the presence of Congo red, although immune complexes formed by these antibodies fail to trigger the complement cascade.This indicates that binding of antibodies to the antigen may not, by itself, fulfill the necessary conditions to generate the signal which triggers effector activity.These findings, together with the results of molecular dynamics simulation studies, enable us to conclude that, apart from the necessary assembling of antibodies, intramolecular structural changes generated by strains which associate high- affinity bivalent antibody fitting to antigen determinants are also required to cross the complement activation threshold.

View Article: PubMed Central - PubMed

Affiliation: .

ABSTRACT
Micellar structures formed by self-assembling Congo red molecules bind to proteins penetrating into function-related unstable packing areas. Here, we have used Congo red--a supramolecular protein ligand--to investigate how the intramolecular structural changes that take place in antibodies following antigen binding lead to complement activation. According to our findings, Congo red binding significantly enhances the formation of antigen-antibody complexes. As a result, even low-affinity transiently binding antibodies can participate in immune complexes in the presence of Congo red, although immune complexes formed by these antibodies fail to trigger the complement cascade. This indicates that binding of antibodies to the antigen may not, by itself, fulfill the necessary conditions to generate the signal which triggers effector activity. These findings, together with the results of molecular dynamics simulation studies, enable us to conclude that, apart from the necessary assembling of antibodies, intramolecular structural changes generated by strains which associate high- affinity bivalent antibody fitting to antigen determinants are also required to cross the complement activation threshold.

Show MeSH