Mevinolin, a fungal metabolite, was isolated from cultures of Aspergillus terreus. The structure and absolute configuration of mevinolm and its open acid form, mevinolinic acid, were determined by a combination of physical techniques.

Intensity controlled interval training increases cardiomyocyte contractility. Higher myofilament Ca(2+)-sensitivity, and enhanced Ca(2+)-handling and pH-regulation are putative mechanisms. Our results suggest that physical exercise induces adaptive hypertrophy in cardiac myocytes with improved contractile function.

Cardiac ryanodine receptors (RyR2s) play a critical role in excitation-contraction coupling by providing a pathway for the release of Ca(2+) from the sarcoplasmic reticulum into the cytosol. RyR2s exist as macromolecular complexes that are regulated via binding of Ca(2+) and protein phosphorylation/dephosphorylation. The present study examined the association of endogenous CaMKII (calcium/calmodulin-dependent protein kinase II) with the RyR2 complex and whether this enzyme could modulate RyR2 function in isolated rabbit ventricular myocardium. Endogenous phosphorylation of RyR2 was verified using phosphorylation site-specific antibodies. Co-immunoprecipitation studies established that RyR2 was physically associated with CaMKIIdelta. Quantitative assessment of RyR2 protein was performed by [(3)H]ryanodine binding to RyR2 immunoprecipitates. Parallel kinase assays allowed the endogenous CaMKII activity associated with these immunoprecipitates to be expressed relative to the amount of RyR2. The activity of RyR2 in isolated cardiac myocytes was measured in two ways: (i) RyR2-mediated Ca(2+) release (Ca(2+) sparks) using confocal microscopy and (ii) Ca(2+)-sensitive [(3)H]ryanodine binding. These studies were performed in the presence and absence of AIP (autocamtide-2-related inhibitory peptide), a highly specific inhibitor of CaMKII. At 1 microM AIP Ca(2+) spark duration, frequency and width were decreased significantly. Similarly, 1 microM AIP decreased [(3)H]ryanodine binding. At 5 microM AIP, a more profound inhibition of Ca(2+) sparks and a decrease in [(3)H]ryanodine binding was observed. Separate measurements showed that AIP (1-5 microM) did not affect sarcoplasmic reticulum Ca(2+)-ATPase-mediated Ca(2+) uptake. These results suggest the existence of an endogenous CaMKIIdelta that associates directly with RyR2 and specifically modulates RyR2 activity.

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Ca2+ release from the sarcoplasmic reticulum (SR) by the IP3 receptors (IP3Rs) crucially regulates diverse cell signalling processes from reproduction to apoptosis. Release from the IP3R may be modulated by endogenous proteins associated with the receptor, such as the 12 kDa FK506-binding protein (FKBP12), either directly or indirectly by inhibition of the phosphatase calcineurin. Here, we report that, in addition to calcineurin, FKPBs modulate release through the mammalian target of rapamycin (mTOR), a kinase that potentiates Ca2+ release from the IP3R in smooth muscle. The presence of FKBP12 was confirmed in colonic myocytes and co-immunoprecipitated with the IP3R. In aortic smooth muscle, however, although present, FKBP12 did not co-immunoprecipitate with IP3R. In voltage-clamped single colonic myocytes rapamycin, which together with FKBP12 inhibits mTOR (but not calcineurin), decreased the rise in cytosolic Ca2+ concentration ([Ca2+]c) evoked by IP3R activation (by photolysis of caged IP3), without decreasing the SR luminal Ca2+ concentration ([Ca2+]l) as did the mTOR inhibitors RAD001 and LY294002. However, FK506, which with FKBP12 inhibits calcineurin (but not mTOR), potentiated the IP3-evoked [Ca2+]c increase. This potentiation was due to the inhibition of calcineurin; it was mimicked by the phosphatase inhibitors cypermethrin and okadaic acid. The latter two inhibitors also prevented the FK506-evoked increase as did a calcineurin inhibitory peptide (CiP). In aortic smooth muscle, where FKBP12 was not associated with IP3R, the IP3-mediated Ca2+ release was unaffected by FK506 or rapamycin. Together, these results suggest that FKBP12 has little direct effect on IP3-mediated Ca2+ release, even though it is associated with IP3R in colonic myocytes. However, FKBP12 might indirectly modulate Ca2+ release through two effector proteins: (1) mTOR, which potentiates and (2) calcineurin, which inhibits Ca2+ release from IP3R in smooth muscle

Mitogen-activated protein kinase phosphatase-2 (MKP-2The amplitude and duration of MAP kinase signaling within a specific subcellular compartment are key features in the integration of extracellular stimuli and their effects on cellular (1). Three main MAP kinase groups, the ERKs, JNK, and p38 MAP kinases, are involved in regulating functions such as proliferation, apoptosis, and differentiation in response to growth factors, peptide hormones, stress, and infection (2). Perturbations in MAP kinase signaling are features of several different types of diseases including several types of cancers (3), diabetes (4), atherosclerosis (5, 6), and immune disorders.The kinetics of MAP kinase activation are strictly controlled principally by the mitogen-activated protein kinase phosphatases (MKPs), 3 a family of at least 10 dual specific phosphatases (DUSPs) that function to terminate MAP kinase signaling within a defined subcellular location (7). They share a common C-terminal catalytic domain and an N-terminal non-catalytic domain containing the MAP kinase interaction motif (8). Each isoform has unique yet overlapping features including substrate specificity, subcellular distribution, and factors regulating induction. For example, MKP-1 is a nuclear DUSP of the type 1 class and selective for all three major MAP kinases in vitro, whereas MKP-3, a type II DUSP, is a cytosolic phosphatase selective solely for ERK over the other kinases (7). Due to effects upon MAP kinase signaling, pertubations in the MKPs have been implicated principally in cancer (9). However, more recently, a role has been established in inflammation (10) and some cardiovascular disorders (11).One poorly studied MKP is MKP-2 (12). This DUSP (DUSP-4) is a member of the type 1 family and has been shown to be induced in response to a number of stimuli including phorbol esters and growth hormones (12-14). Nuclear targeting is regulated by two distinct nuclear targeting sequences (15). Substrate specificity for ERK and JNK was originally demonstrated in vitro (16); however, selective inhibition of JNK has been implicated in cellular studies (17,18). Although MKP-2 has been recently regarded as a surrogate for the more well described MKP-1, recent cellular studies demonstrate a role in protection against apoptosis (17) and in senescence (19). However, there is still a lack of information describing the function of DUSP-4 in different cell types, in particular regarding substrate selectivity in vivo.We have recently developed a DUSP-4 deletion mouse model and demonstrated a novel immunological phenotype in vivo (20). Using embryonic fibroblasts from DUSP-4 deletion mice, we now examine the effect of deletion upon MAP kinase signaling and growth parameters. We find that despite very moderate increases in ERK and JNK activity, MKP-2 deletion has profound effects upon cellular proliferation. In particular, we identify a role for MKP-2 in G 2 /M phase transition and demonstrate that MKP-2 plays a role in cell survival in response to the apo-* This work was supporte...

Journal of Physiologyventricle in rabbit heart 8-9 weeks after an experimentally induced apical infarct, and compares these values with equivalent measurements from sham-operated (sham) hearts.