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Mechanism of Focal Adhesion Kinase Mechanosensing.

Zhou J, Aponte-Santamaría C, Sturm S, Bullerjahn JT, Bronowska A, Gräter F - PLoS Comput. Biol. (2015)

Bottom Line: Tensile forces, propagating from the membrane through the PIP2 binding site of the FERM domain and from the cytoskeleton-anchored FAT domain, activate FAK by unlocking its central phosphorylation site (Tyr576/577) from the autoinhibitory FERM domain.Varying loading rates, pulling directions, and membrane PIP2 concentrations corroborate the specific opening of the FERM-kinase domain interface, due to its remarkably lower mechanical stability compared to the individual alpha-helical domains and the PIP2-FERM link.Analyzing downstream signaling networks provides further evidence for an intrinsic mechano-signaling role of FAK in broadcasting force signals through Ras to the nucleus.

View Article: PubMed Central - PubMed

Affiliation: Heidelberg Institute for Theoretical Studies, Heidelberg, Germany.

ABSTRACT
Mechanosensing at focal adhesions regulates vital cellular processes. Here, we present results from molecular dynamics (MD) and mechano-biochemical network simulations that suggest a direct role of Focal Adhesion Kinase (FAK) as a mechano-sensor. Tensile forces, propagating from the membrane through the PIP2 binding site of the FERM domain and from the cytoskeleton-anchored FAT domain, activate FAK by unlocking its central phosphorylation site (Tyr576/577) from the autoinhibitory FERM domain. Varying loading rates, pulling directions, and membrane PIP2 concentrations corroborate the specific opening of the FERM-kinase domain interface, due to its remarkably lower mechanical stability compared to the individual alpha-helical domains and the PIP2-FERM link. Analyzing downstream signaling networks provides further evidence for an intrinsic mechano-signaling role of FAK in broadcasting force signals through Ras to the nucleus. This distinguishes FAK from hitherto identified focal adhesion mechano-responsive molecules, allowing a new interpretation of cell stretching experiments.

No MeSH data available.


Related in: MedlinePlus

Mechanism of FK-FAK mechanical activation.A) Interfacial area between the F2- and C-lobe (grey) and average force exerted by the two springs (blue) as a function of the distance between springs, Dspring. Results from six independent FPMD simulations are shown: (1–3) without the membrane pulling at V = 0.006, 0.006 and 0.014 nm/ns, respectively, and (4 and 5) pulling diagonally away from the membrane at V = 0.03 and 0.05 nm/ns, respectively. The interfacial area drops from initial values of 3–4.5 nm2 to intermediate values of 1.5–2.8 nm2. Afterwards it decreases to zero. Rupture force (highest force peak) always corresponded to the first drop in the interfacial area (red line). The peak force associated to the second drop in the area is highlighted with the green line. B) Distribution of interface areas reflecting the two states of FK-FAK during its force-induced opening (highlighted with arrows). All FPMD simulations were considered to compute the distribution. C) Residues involved in the rupture steps are highlighted as sticks. FERM F2- and Kinase C-lobe are shown in surface representation. Rupture steps are associated to the disruption of hydrophobic interactions (green); salt bridges (blue) and other electrostatic interactions (magenta), and interactions with other partners (cyan). Residues were identified by TRFDA (S5 Fig). They are listed in S2 Table.
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pcbi.1004593.g003: Mechanism of FK-FAK mechanical activation.A) Interfacial area between the F2- and C-lobe (grey) and average force exerted by the two springs (blue) as a function of the distance between springs, Dspring. Results from six independent FPMD simulations are shown: (1–3) without the membrane pulling at V = 0.006, 0.006 and 0.014 nm/ns, respectively, and (4 and 5) pulling diagonally away from the membrane at V = 0.03 and 0.05 nm/ns, respectively. The interfacial area drops from initial values of 3–4.5 nm2 to intermediate values of 1.5–2.8 nm2. Afterwards it decreases to zero. Rupture force (highest force peak) always corresponded to the first drop in the interfacial area (red line). The peak force associated to the second drop in the area is highlighted with the green line. B) Distribution of interface areas reflecting the two states of FK-FAK during its force-induced opening (highlighted with arrows). All FPMD simulations were considered to compute the distribution. C) Residues involved in the rupture steps are highlighted as sticks. FERM F2- and Kinase C-lobe are shown in surface representation. Rupture steps are associated to the disruption of hydrophobic interactions (green); salt bridges (blue) and other electrostatic interactions (magenta), and interactions with other partners (cyan). Residues were identified by TRFDA (S5 Fig). They are listed in S2 Table.

Mentions: We then identified the first steps along the opening motion of FK-FAK giving rise to rupture forces. Fig 3A shows typical force profiles and F2/C-lobe interaction areas as a function of the spring locations recovered from the FPMD simulations. For both FK-FAK in isolation and bound to the membrane, and independent of the loading rate, we observed that the interface area between the two lobes was reduced in two steps, both of which coincided with noticeable force peaks. The maximal force was reached when the first decrease in inter-lobe area occurred (from 3–4.5 nm2 to 1.5–2.8 nm2). This led to a short-lived intermediate, as reflected by a second peak in the distribution of the F2/C-lobe interface area (Fig 3B), before the two lobes fully dissociated. We note that the intermediate becomes less evident for faster pulling velocities.


Mechanism of Focal Adhesion Kinase Mechanosensing.

Zhou J, Aponte-Santamaría C, Sturm S, Bullerjahn JT, Bronowska A, Gräter F - PLoS Comput. Biol. (2015)

Mechanism of FK-FAK mechanical activation.A) Interfacial area between the F2- and C-lobe (grey) and average force exerted by the two springs (blue) as a function of the distance between springs, Dspring. Results from six independent FPMD simulations are shown: (1–3) without the membrane pulling at V = 0.006, 0.006 and 0.014 nm/ns, respectively, and (4 and 5) pulling diagonally away from the membrane at V = 0.03 and 0.05 nm/ns, respectively. The interfacial area drops from initial values of 3–4.5 nm2 to intermediate values of 1.5–2.8 nm2. Afterwards it decreases to zero. Rupture force (highest force peak) always corresponded to the first drop in the interfacial area (red line). The peak force associated to the second drop in the area is highlighted with the green line. B) Distribution of interface areas reflecting the two states of FK-FAK during its force-induced opening (highlighted with arrows). All FPMD simulations were considered to compute the distribution. C) Residues involved in the rupture steps are highlighted as sticks. FERM F2- and Kinase C-lobe are shown in surface representation. Rupture steps are associated to the disruption of hydrophobic interactions (green); salt bridges (blue) and other electrostatic interactions (magenta), and interactions with other partners (cyan). Residues were identified by TRFDA (S5 Fig). They are listed in S2 Table.
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pcbi.1004593.g003: Mechanism of FK-FAK mechanical activation.A) Interfacial area between the F2- and C-lobe (grey) and average force exerted by the two springs (blue) as a function of the distance between springs, Dspring. Results from six independent FPMD simulations are shown: (1–3) without the membrane pulling at V = 0.006, 0.006 and 0.014 nm/ns, respectively, and (4 and 5) pulling diagonally away from the membrane at V = 0.03 and 0.05 nm/ns, respectively. The interfacial area drops from initial values of 3–4.5 nm2 to intermediate values of 1.5–2.8 nm2. Afterwards it decreases to zero. Rupture force (highest force peak) always corresponded to the first drop in the interfacial area (red line). The peak force associated to the second drop in the area is highlighted with the green line. B) Distribution of interface areas reflecting the two states of FK-FAK during its force-induced opening (highlighted with arrows). All FPMD simulations were considered to compute the distribution. C) Residues involved in the rupture steps are highlighted as sticks. FERM F2- and Kinase C-lobe are shown in surface representation. Rupture steps are associated to the disruption of hydrophobic interactions (green); salt bridges (blue) and other electrostatic interactions (magenta), and interactions with other partners (cyan). Residues were identified by TRFDA (S5 Fig). They are listed in S2 Table.
Mentions: We then identified the first steps along the opening motion of FK-FAK giving rise to rupture forces. Fig 3A shows typical force profiles and F2/C-lobe interaction areas as a function of the spring locations recovered from the FPMD simulations. For both FK-FAK in isolation and bound to the membrane, and independent of the loading rate, we observed that the interface area between the two lobes was reduced in two steps, both of which coincided with noticeable force peaks. The maximal force was reached when the first decrease in inter-lobe area occurred (from 3–4.5 nm2 to 1.5–2.8 nm2). This led to a short-lived intermediate, as reflected by a second peak in the distribution of the F2/C-lobe interface area (Fig 3B), before the two lobes fully dissociated. We note that the intermediate becomes less evident for faster pulling velocities.

Bottom Line: Tensile forces, propagating from the membrane through the PIP2 binding site of the FERM domain and from the cytoskeleton-anchored FAT domain, activate FAK by unlocking its central phosphorylation site (Tyr576/577) from the autoinhibitory FERM domain.Varying loading rates, pulling directions, and membrane PIP2 concentrations corroborate the specific opening of the FERM-kinase domain interface, due to its remarkably lower mechanical stability compared to the individual alpha-helical domains and the PIP2-FERM link.Analyzing downstream signaling networks provides further evidence for an intrinsic mechano-signaling role of FAK in broadcasting force signals through Ras to the nucleus.

View Article: PubMed Central - PubMed

Affiliation: Heidelberg Institute for Theoretical Studies, Heidelberg, Germany.

ABSTRACT
Mechanosensing at focal adhesions regulates vital cellular processes. Here, we present results from molecular dynamics (MD) and mechano-biochemical network simulations that suggest a direct role of Focal Adhesion Kinase (FAK) as a mechano-sensor. Tensile forces, propagating from the membrane through the PIP2 binding site of the FERM domain and from the cytoskeleton-anchored FAT domain, activate FAK by unlocking its central phosphorylation site (Tyr576/577) from the autoinhibitory FERM domain. Varying loading rates, pulling directions, and membrane PIP2 concentrations corroborate the specific opening of the FERM-kinase domain interface, due to its remarkably lower mechanical stability compared to the individual alpha-helical domains and the PIP2-FERM link. Analyzing downstream signaling networks provides further evidence for an intrinsic mechano-signaling role of FAK in broadcasting force signals through Ras to the nucleus. This distinguishes FAK from hitherto identified focal adhesion mechano-responsive molecules, allowing a new interpretation of cell stretching experiments.

No MeSH data available.


Related in: MedlinePlus