Altered PKC expression and phosphorylation in response to the nature, direction, and magnitude of mechanical stretch

2007 ◽  
Vol 85 (2) ◽  
pp. 243-250 ◽  
Author(s):  
Tara A. Bullard ◽  
Joshua L. Hastings ◽  
Jeffrey M. Davis ◽  
Thomas K. Borg ◽  
Robert L. Price

Protein kinase C (PKC) isozymes have been shown to play a role in mechanotransduction in a variety of cell types. We sought to identify the PKC isozymes involved in transducing mechanical (cyclic vs. static), direction and intensity of stretch by examining changes in protein expression and phosphorylation. We used a 3-dimensional culture system with aligned neonatal rat cardiac myocytes on silastic membranes. Myocytes were subjected to either cyclic stretch at 5 cycles/min or static stretch for a period of 24 h at intensities of 0%, 2.5%, 5%, or 10% of full membrane length. Stretch was applied in perpendicular or parallel directions to myocyte alignment. PKC δ was most sensitive to stretch applied perpendicular to myocyte alignment regardless of the nature of stretch, while phospho PKC δ T505 increased in response to static-perpendicular stretch. PKC ε expression was altered by cyclic stretch but not static stretch, while phospho PKC ε S719 remained unchanged. PKC α expression was not altered by stretch; however, phospho PKC α S657 increased in a dose-dependent manner following cyclic-perpendicular stretch. Our results indicate that changes in PKC expression and phosphorylation state may be a mechanism for cardiac myocytes to discriminate between the nature, direction, and intensity of mechanical stretch.

Author(s):  
Kayleigh G. Marsh ◽  
Adrian Arrieta ◽  
Donna J. Thuerauf ◽  
Erik A. Blackwood ◽  
Lauren MacDonnell ◽  
...  

While peroxisomes have been extensively studied in other cell types, their presence and function have gone virtually unexamined in cardiac myocytes. Here, in neonatal rat ventricular myocytes (NRVM) we showed that several known peroxisomal proteins co-localize to punctate structures with a morphology typical of peroxisomes. Surprisingly, we found that the peroxisomal protein, fatty acyl-CoA reductase 1 (FAR1), was upregulated by chemical and pathophysiological ER stress induced by tunicamycin (TM) and simulated ischemia/reperfusion (sI/R), respectively. Moreover, FAR1 induction in NRVM was mediated by the ER stress-sensor, activating transcription factor 6 (ATF6). Functionally, FAR1 knockdown reduced myocyte death during oxidative stress induced by either sI/R or hydrogen peroxide (H2O2). Thus, Far1 is an ER stress-inducible gene, which encodes a protein that localizes to peroxisomes of cardiac myocytes, where it reduces myocyte viability during oxidative stress. Since FAR1 is critical for plasmalogen synthesis, these results imply that plasmalogens may exert maladaptive effects on the viability of myocytes exposed to oxidative stress.


1999 ◽  
Vol 5 (3) ◽  
pp. 44
Author(s):  
Toshihiro Tsuruda ◽  
Johji Kato ◽  
Kazuo Kitamura ◽  
Takuroh Imamura ◽  
Yasushi Koiwaya ◽  
...  

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Yoshiaki Ohyama ◽  
Toru Tanaka ◽  
Takehisa Shimizu ◽  
Hiroshi Doi ◽  
Norimichi Koitabashi ◽  
...  

Backgroud: Recent studies demonstrated non-hematopoietical effects of Erythropoietin (Epo) and its receptor (EpoR) in a variety of tissues including cardiovascular system. Epo treatment improves cardiac function in patients with heart failure and reduces infarct size after ischemia/reperfusion injury in the heart. However, little attention has been paid for the endogenous regulatory mechanisms regulating EpoR expression. In this study, we hypothesize that B-type natriuretic peptide upregulates EpoR gene expression in failing heart. Methods and Results: Wister rats underwent transverse aortic constriction surgery to induce hypertrophy. RT-PCR analyses of those rats showed that EpoR mRNA levels were increased in the left ventricle and positively correlated with the levels of BNP mRNA (n=10, r=0.67, p<0.05). Next we examined the expression of EpoR in human failing heart by using autopsy specimens and found that EpoR mRNA levels were significantly elevated in patients with dilated cardiomyopathy compared with those in normal heart. Immunohistochemistry of endomyocardial biopsy specimens of failing heart (n=54) showed that EpoR mRNA levels were correlated with severity of cardiac dysfunction estimated by diameter of cardiac chambers, pathomorphology, serum BNP concentration and functional class of New York Heart Association. Interestingly, stimulation of cultured neonatal rat cardiac myocytes with BNP, but not with hypertrophic reagents including endothelin I, angiotensin II and norepinephrine, significantly increased the EpoR mRNA levels in a time-dependent manner. Overexpression of cGMP-dependent protein kinase (PKG) increased EpoR transcript in cultured cardiac myocytes. BNP-induced EpoR expression was abrogated in the presence of KT5823, a specific inhibitor for PKG. Conclusion: These results suggest a role for BNP in mediating an induction of EpoR expression in failing myocardium and indicate that the cardiac EpoR gene is a target of cGMP/PKG signaling.


2007 ◽  
Vol 293 (1) ◽  
pp. H677-H683 ◽  
Author(s):  
Betty S. Hu ◽  
Lee K. Landeen ◽  
Nakon Aroonsakool ◽  
Wayne R. Giles

Mechanical force can induce a number of fundamental short- and long-term responses in myocardium. These include alterations in ECM, activation of cell-signaling pathways, altered gene regulation, changes in cell proliferation and growth, and secretion of a number of peptides and growth factors. It is now known that a number of these autocrine/paracrine factors are secreted from both cardiomyocytes and ventricular cardiac fibroblasts (CFb) in response to stretch. One such substance is IGF-I. IGF-I is an important autocrine/paracrine factor that can regulate physiological or pathophysiological responses, such as hypertrophy. In this study, we addressed the possible effects of mechanical perturbation, biaxial strain, on IGF-I secretion from adult rat CFb. CFb were subjected to either static stretch (3–10%) or cyclic stretch (10%; 0.1–1 Hz) over a 24-h period. IGF-1 secretion from CFb in response to selected stretch paradigms was examined using ELISA to measure IGF-I concentrations in conditioned media. Static stretch did not result in any measurable modulation of IGF-I secretion from CFb. However, cyclic stretch significantly increased IGF-I secretion from CFb in a frequency- and time-dependent manner compared with nonstretched controls. This stretch-induced increase in secretion was relatively insensitive to changes in extracellular [Ca2+] or to block of L-type Ca2+ channels. In contrast, thapsigargin, an inhibitor of sarco(endo)plasmic reticulum Ca2+ ATPase, remarkably decreased stretch-induced IGF-I secretion from CFb. We further show that IGF-I can upregulate mRNA expression of atrial natriuretic peptide in myocytes. In summary, cyclic stretch can significantly increase IGF-I secretion from CFb, and this effect is dependent on a thapsigargin-sensitive pool of intracellular [Ca2+].


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