Erik Swanson

The time course of the response and recovery after acute activity seen in exercise is not well understood. The goal of this work is to address how proteins of the thin filament (actin and its capping protein CapZ) are changed by 1 h of mechanical stimulation and return to baseline over time. Neonatal rat ventricular myocytes in culture were subjected to cyclic 10% strain at 1 Hz for 1 h to mimic increased mechanical loading during exercise. CapZ and actin dynamics were analyzed by fluorescence… Show more

The time course of the response and recovery after acute activity seen in exercise is not well understood. The goal of this work is to address how proteins of the thin filament (actin and its capping protein CapZ) are changed by 1 h of mechanical stimulation and return to baseline over time. Neonatal rat ventricular myocytes in culture were subjected to cyclic 10% strain at 1 Hz for 1 h to mimic increased mechanical loading during exercise. CapZ and actin dynamics were analyzed by fluorescence recovery after photobleaching (FRAP) using CapZβ1-GFP, actin-GFP, or actin-RFP. After cyclic strain, CapZ dynamics increased above resting controls and abated 2-3 h after cessation of the cyclic strain. Similarly, actin dynamics initially increased and abated 1.5-2 h after the end of stimulation. Neurohormonal hypertrophic stimulation by phenylephrine or norepinephrine treatments also elevated actin dynamics but required a much longer time of treatment (24-48 h) to be detectable. The actin capping mechanism was explored by use of expression of CapZβ1 with a COOH-terminal deletion (CapZβ1ΔC). Increased dynamics of actin seen with CapZβ1ΔC was similar to the response to cyclic strain. Thus it is possible that mechanical stimulation alters the dynamics for CapZ capping of the actin filament through the CapZβ1 COOH terminus, known as the β tentacle, thereby remodeling sarcomeres in cardiac myocytes. This adaptive mechanism, which is probably regulating thin-filament addition, declines a few hours after the end of a bout of exercise. Show less

The time course of the response and recovery after acute activity seen in exercise is not well understood. The goal of this work is to address how proteins of the thin filament (actin and its capping protein, CapZ) are changed by one hour of mechanical stimulation and return to baseline over time. Neonatal rat ventricular myocytes in culture were subjected to cyclic 10% strain at 1 Hz for 1 hr to mimic increased mechanical loading during exercise. CapZ and actin dynamics were analyzed by… Show more

The time course of the response and recovery after acute activity seen in exercise is not well understood. The goal of this work is to address how proteins of the thin filament (actin and its capping protein, CapZ) are changed by one hour of mechanical stimulation and return to baseline over time. Neonatal rat ventricular myocytes in culture were subjected to cyclic 10% strain at 1 Hz for 1 hr to mimic increased mechanical loading during exercise. CapZ and actin dynamics were analyzed by fluorescence recovery after photobleaching (FRAP) using CapZβ1-GFP, actin-GFP or actin-RFP. After cyclic strain, CapZ dynamics increased above resting controls, and abated 2-3 hr after cessation of the cyclic strain. Similarly, actin dynamics initially increased, and abated 1.5-2 hr after the end of stimulation. Neurohormonal hypertrophic stimulation by phenylephrine or norepinephrine treatments also elevated actin dynamics but required a much longer time of treatment (24-48 hr) to be detectable. The actin capping mechanism was explored by use of expression of CapZβ1 with a C-terminal deletion (CapZβ1C). Increased dynamics of actin seen with CapZβ1C was similar to the response to cyclic strain. Thus, it is possible that mechanical stimulation alters the dynamics for CapZ capping of the actin filament through the CapZβ1 C-terminus, known as the β tentacle, thereby remodeling sarcomeres in cardiac myocytes. This adaptive mechanism, which is probably regulating thin filament addition, declines a few hours after the end of a bout of exercise. Show less

A spread in the Columbia Public Health Magazine about my experiences and work at New York Presbyterian Hospital. Magazine pages: 40-41.

The mechanisms of sarcomere remodeling in cardiomyocyte hypertrophy are complex, and our previous studies have identified an important role for protein kinase C-ε (PKCε) and the f-actin capping protein CapZ in this process. We now hypothesize that CapZ undergoes PKCε-dependent post-translational modification, which affects its binding kinetics in response to cyclic mechanical strain (CS). Neonatal rat ventricular myocytes were subjected to 10% CS at 1Hz for 1h. CapZ dissociation rates were… Show more

The mechanisms of sarcomere remodeling in cardiomyocyte hypertrophy are complex, and our previous studies have identified an important role for protein kinase C-ε (PKCε) and the f-actin capping protein CapZ in this process. We now hypothesize that CapZ undergoes PKCε-dependent post-translational modification, which affects its binding kinetics in response to cyclic mechanical strain (CS). Neonatal rat ventricular myocytes were subjected to 10% CS at 1Hz for 1h. CapZ dissociation rates were analyzed by fluorescence recovery after photobleaching (FRAP) using adenoviruses expressing wildtype (wt) GFP-CapZβ1 or wt GFP-CapZβ2. To examine the role of PKCε-dependent post-translational modification of CapZ, cells were infected (100 moi, 24h) with adenoviruses expressing dominant-negative (dn) or constitutively active (ca) PKCε prior to CS. CS enhanced dissociation rates for CapZβ1 (196%, P<0.05) above resting controls, but CapZβ2 was unchanged. caPKCε significantly enhanced dissociation rates for CapZβ1 above controls (176%, P<0.05). Additionally, CapZ post-translational modifications were investigated with quantitative two-dimensional gel electrophoresis (2DGE). 2DGE western blotting identified two post-translational modifications of CapZβ1 and one of CapZβ2. Cyclic strain deceased the unmodified form of CapZβ1 (P<0.05) and increased the doubly modified form (P<0.05) compared to controls, while the addition of dnPKCε with CS reversed this effect (P>0.05). Treatment of caPKCε on unstretched cells increased the singly modified form compared to controls (P<0.05). Taken together, our data strongly suggests that CS produces post-translational modification of CapZβ1 but not of CapZβ2. Furthermore, since caPKCε modifies the post-translational profile of CapZβ1 differently from mechanical stress, other mechanisms must also be operative. Show less