Katsuhito Takahashi

Caldesmon150 regulates the tropomyosin-enhanced actin-myosin interaction in gizzard smooth muscle

Using a reconstituted system in which myosin was preferentially phosphorylated, we examined the regulatory action of caldesmon150 on the smooth muscle actin-myosin interaction. Caldesmon150 inhibited the tropomyosin-enhanced actomyosin ATPase activity in a Ca2+-independent manner. This inhibitory effect of caldesmon150 was observed to be overcome by the addition of calmodulin in a Ca2+-dependent manner. In accordance with the observations of ATPase activity, we demonstrated evidence that the regulatory action of caldesmon150 on the actin site was mainly through control of the tropomyosin-enhanced actin-myosin interaction and calmodulin confers the Ca2+-sensitivity upon the caldesmon150 action determined by the cosedimentation method.

Do thin filaments of smooth muscle contain calponin?: A new method for the preparation

A new method for the preparation of smooth muscle thin filaments which include calponin was established. We found that calponin readily separated from thin filaments in the presence of 10 mM ATP. By preventing thin filament extract from exposing to ATP, we obtained thin filaments which contained actin, tropomyosin, caldesmon and calponin in molar ratios of 7:0.9:0.6:0.7. We studied myosin Mg‐ATPase activity by using the thin filaments in comparison with classical thin filaments prepared by the method of Marston and Smith, which contained the same amounts of caldesmon and tropomyosin as our thin filaments but lost almost all calponin. The presence of calponin reduced the V max value for thin filament‐activated myosin Mg‐ATPase activity by 33% without a significant change in K m value. These findings suggest that calponin inhibits myosin Mg‐ATPase activity by modulation of a kinetic step as an integral component of smooth muscle thin filaments.

Crosslinking of actin filaments is caused by caldesmon aggregates, but not by its dimers

Caldesmon Actin‐associated protein Calmodulin‐binding protein Actin‐crosslinker Chicken gizzard

Loss of smooth muscle calponin results in impaired blood vessel maturation in the tumor-host microenvironment.

The interactions between malignant cells and the microenvironment of the local host tissue play a critical role in tumor growth, metastasis and their response to treatment modalities. We investigated the roles of smooth muscle calponin (Cnn1, also called calponin h1 or basic calponin) in the development of tumor vascul ature in vivo by analyzing mutant mice lacking the Cnn1 gene. Here we show that loss of Cnn1 in host mural cells prevents maturation of tumor vasculature. In vitro studies showed that platelet‐derived growth factor B‐induced vascular smooth muscle migration was downregulated by the Cnn1‐deficiency, and forced expression of Cnn1 restored migration. Moreover, destruction of established tumor mass by treatment with an antivascular endothelial growth factor antibody was markedly enhanced in Cnn1‐deficient mice. These data, coupled with the knowledge that structural fragility of normal blood vessels is caused by loss of the Cnn1 gene, suggest that Cnn1 plays an important role in the maturation of blood vessels, and may have implications for therapeutic strategies targeting tumor vasculature for treatment of human cancers. (Cancer Sci 2007; 98: 757–763)

Effects of h1-calponin ablation on the contractile properties of bladder versus vascular smooth muscle in mice lacking SM-B myosin

The functional significance of smooth muscle‐specific h1‐calponin up‐regulation in the smooth muscle contractility of SM‐B null mice was studied by generating double knockout mice lacking both h1‐calponin and SM‐B myosin. The double knockout mice appear healthy, reproduce well and do not show any smooth muscle pathology. Loss of h1‐calponin in the SM‐B null mice bladder resulted in increased maximal shortening velocity (Vmax) and steady‐state force generation. The force dilatation pressure, which was decreased in the SM‐B null mesenteric vessels, was restored to wild‐type levels in the double knockout vessels. In contrast, the half‐time to maximal constriction was significantly increased in the double knockout vessels similar to that of SM‐B null mice and indicating decreased shortening velocity in the double knockout vessels. Biochemical analyses showed that there is a significant reduction in smooth muscle α‐actin levels, whereas h‐caldesmon levels are increased in the double knockout bladder and mesenteric vessels, suggesting that these changes may also partly contribute to the altered contractile function. Taken together, our studies suggest that up‐regulation of h1‐calponin in the SM‐B null mice may be necessary to maintain a reduced level of cross‐bridge cycling over time in the absence of SM‐B myosin and play an important role in regulating the smooth muscle contraction.

A Single-Center, Open-Label, Randomized, Parallel-Group Study Assessing the Differences Between an Angiotensin II Receptor Antagonist and an Angiotensin-Converting Enzyme Inhibitor in Hypertensive Patients with Congestive Heart Failure: The Research for Efficacy of Angiotensin II Receptor Antagonist in Hypertensive Patients with Congestive Heart Failure Study

BACKGROUNDnAngiotensin II receptor blockers (ARBs) and angiotensin-converting enzyme inhibitors (ACEIs) have been used to treat congestive heart failure (CHF). According to a MEDLINE search, however, few studies are available on the clinical differences between ARBs and ACEIs in CHF.nnnOBJECTIVEnTo examine the clinical differences between an ARB (candesartan cilexetil) and an ACEI (lisinopril) in the treatment of CHF, we investigated exercise capacity, ventricular function, and neurohormonal levels in hypertensive patients with CHF before and after treatment with these agents.nnnMETHODSnPatients with symptoms of CHF (New York Heart Association functional class II-III and left ventricular ejection fraction [LVEF] ≤45%) complicated by hypertension (systolic blood pressure [BP] ≥140 mm Hg or diastolic BP ≥90 mm Hg) were eligible for this single-center, open-label, randomized, parallel-group study. They were given either the ARB or the ACEI for 24 weeks. A cardiopulmonary exercise test and echocardiography were performed. Clinical findings and cardiac events in addition to the CHF symptoms were investigated. Neurohormonal levels were measured before and after 24 weeks of treatment with the study drug. The primary end point of this study was exercise capacity, which was measured using peak oxygen consumption (VO2).nnnRESULTSnForty-two patients with CHF were enrolled and 38 (28 men, 10 women; mean [SD] age, 69.0 [8.2] years) completed the study. None of these patients had definite progression of the CHF symptoms. In the ARB-treated patients, mean (SD) peak VO2 (mL/min/kg) and LVEF (%) increased from 14.1 (2.9) to 15.3 (3.4) and from 34.4 (9.5) to 41.8 (9.5), respectively. In the ACEI group, the peak VO2 did not change, but the LVEF (%) increased from 34.2 (10.2) to 40.4 (13.0). However, the differences between ARB and ACEI were not clarified because of the possibility of a small sample size.nnnCONCLUSIONSnAlthough this study was not powered to show differences in efficacy between the ARB and ACEI in this study, our findings suggest that both ARB and ACEI had beneficial effects in hypertensive patients with CHF. Some unidentified differences in hemodynamic characteristics were found between the ARB and the ACEI groups.