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Articles by M. E Anderson
Total Records ( 4 ) for M. E Anderson
  C. A Witczak , N Jessen , D. M Warro , T Toyoda , N Fujii , M. E Anderson , M. F Hirshman and L. J. Goodyear
 

Studies using chemical inhibitors have suggested that the Ca2+-sensitive serine/threonine kinase Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a key regulator of both insulin- and contraction-stimulated glucose uptake in skeletal muscle. However, due to nonspecificity of these inhibitors, the specific role that CaMKII may play in the regulation of glucose uptake is not known. We sought to determine whether specific inhibition of CaMKII impairs insulin- and/or contraction-induced glucose uptake in mouse skeletal muscle. Expression vectors containing green fluorescent protein conjugated to a CaMKII inhibitory (KKALHRQEAVDCL) or control (KKALHAQERVDCL) peptide were transfected into tibialis anterior muscles by in vivo electroporation. After 1 wk, muscles were assessed for peptide expression, CaMK activity, insulin- and contraction-induced 2-[3H]deoxyglucose uptake, glycogen concentrations, and changes in intracellular signaling proteins. Expression of the CaMKII inhibitory peptide decreased muscle CaMK activity ~35% compared with control peptide. Insulin-induced glucose uptake was not changed in muscles expressing the inhibitory peptide. In contrast, expression of the inhibitory peptide significantly decreased contraction-induced muscle glucose uptake (~30%). Contraction-induced decreases in muscle glycogen were not altered by the inhibitory peptide. The CaMKII inhibitory peptide did not alter expression of the glucose transporter GLUT4 and did not impair contraction-induced increases in the phosphorylation of AMP-activated protein kinase (Thr172) or TBC1D1/TBC1D4 on phospho-Akt substrate sites. These results demonstrate that CaMKII does not regulate insulin-stimulated glucose uptake in skeletal muscle. However, CaMKII plays a critical role in the regulation of contraction-induced glucose uptake in mouse skeletal muscle.

  W. C Spanos , P Nowicki , D. W Lee , A Hoover , B Hostager , A Gupta , M. E Anderson and J. H. Lee
 

Background  Human papillomavirus (HPV) is the most identifiable cause of head and neck squamous cell cancer (HNSCC). Compared with HPV-negative HNSCC, HPV-positive HNSCC presents at an advanced stage but with significantly better survival. We created a syngeneic mouse model of HPV-positive and HPV-negative HNSCC by transforming mouse primary tonsil epithelial cells with either HPV oncogenes or a nonantigenic RNA interference strategy that affects similar oncogenic pathways.

Objectives  To examine the effect of radiation therapy on HPV-positive and HPV-negative tumors in immune-competent and immune-incompetent mice and to examine responses in human cancer cell lines.

Design  Prospective in vivo murine model.

Main Outcome Measures  Survival and tumor growth.

Results  For human and murine transformed cell lines, HPV-positive cells were more resistant to radiation and cisplatin therapy compared with HPV-negative cells. In vivo, HPV-positive tumors were more sensitive to radiation, with complete clearance at 20 Gy, compared with their HPV-negative counterparts, which showed persistent growth. Cisplatin in vivo cleared HPV-positive tumors but not HPV-negative tumors. However, neither radiation or cisplatin therapy cured immune-incompetent mice. Adoptive transfer of wild-type immune cells into immune-incompetent mice restored HPV-positive tumor clearance with cisplatin therapy.

Conclusions  The HPV-positive tumors are not more curable based on increased epithelial sensitivity to cisplatin or radiation therapy. Instead, radiation and cisplatin induce an immune response to this antigenic cancer. The implications of these results may lead to novel therapies that enhance tumor eradication for HPV-positive cancers.

  H Gudmundsson , T. J Hund , P. J Wright , C. F Kline , J. S Snyder , L Qian , O. M Koval , S. R Cunha , M George , M. A Rainey , F. E Kashef , W Dun , P. A Boyden , M. E Anderson , H Band and P. J. Mohler
 

Rationale: Cardiac membrane excitability is tightly regulated by an integrated network of membrane-associated ion channels, transporters, receptors, and signaling molecules. Membrane protein dynamics in health and disease are maintained by a complex ensemble of intracellular targeting, scaffolding, recycling, and degradation pathways. Surprisingly, despite decades of research linking dysfunction in membrane protein trafficking with human cardiovascular disease, essentially nothing is known regarding the molecular identity or function of these intracellular targeting pathways in excitable cardiomyocytes.

Objective: We sought to discover novel pathways for membrane protein targeting in primary cardiomyocytes.

Methods and Results: We report the initial characterization of a large family of membrane trafficking proteins in human heart. We used a tissue-wide screen for novel ankyrin-associated trafficking proteins and identified 4 members of a unique Eps15 homology (EH) domain–containing protein family (EHD1, EHD2, EHD3, EHD4) that serve critical roles in endosome-based membrane protein targeting in other cell types. We show that EHD1-4 directly associate with ankyrin, provide the first information on the expression and localization of these molecules in primary cardiomyocytes, and demonstrate that EHD1-4 are coexpressed with ankyrin-B in the myocyte perinuclear region. Notably, the expression of multiple EHD proteins is increased in animal models lacking ankyrin-B, and EHD3-deficient cardiomyocytes display aberrant ankyrin-B localization and selective loss of Na/Ca exchanger expression and function. Finally, we report significant modulation of EHD expression following myocardial infarction, suggesting that these proteins may play a key role in regulating membrane excitability in normal and diseased heart.

Conclusions: Our findings identify and characterize a new class of cardiac trafficking proteins, define the first group of proteins associated with the ankyrin-based targeting network, and identify potential new targets to modulate membrane excitability in disease. Notably, these data provide the first link between EHD proteins and a human disease model.

  S Wei , A Guo , B Chen , W Kutschke , Y. P Xie , K Zimmerman , R. M Weiss , M. E Anderson , H Cheng and L. S. Song
  Rationale:

The transverse tubule (T-tubule) system is the ultrastructural substrate for excitation–contraction coupling in ventricular myocytes; T-tubule disorganization and loss are linked to decreased contractility in end stage heart failure (HF).

Objective:

We sought to examine (1) whether pathological T-tubule remodeling occurs early in compensated hypertrophy and, if so, how it evolves during the transition from hypertrophy to HF; and (2) the role of junctophilin-2 in T-tubule remodeling.

Methods and Results:

We investigated T-tubule remodeling in relation to ventricular function during HF progression using state-of-the-art confocal imaging of T-tubules in intact hearts, using a thoracic aortic banding rat HF model. We developed a quantitative T-tubule power (TTpower) index to represent the integrity of T-tubule structure. We found that discrete local loss and global reorganization of the T-tubule system (leftward shift of TTpower histogram) started early in compensated hypertrophy in left ventricular (LV) myocytes, before LV dysfunction, as detected by echocardiography. With progression from compensated hypertrophy to early and late HF, T-tubule remodeling spread from the LV to the right ventricle, and TTpower histograms of both ventricles gradually shifted leftward. The mean LV TTpower showed a strong correlation with ejection fraction and heart weight to body weight ratio. Over the progression to HF, we observed a gradual reduction in the expression of a junctophilin protein (JP-2) implicated in the formation of T-tubule/sarcoplasmic reticulum junctions. Furthermore, we found that JP-2 knockdown by gene silencing reduced T-tubule structure integrity in cultured adult ventricular myocytes.

Conclusions:

T-tubule remodeling in response to thoracic aortic banding stress begins before echocardiographically detectable LV dysfunction and progresses over the development of overt structural heart disease. LV T-tubule remodeling is closely associated with the severity of cardiac hypertrophy and predicts LV function. Thus, T-tubule remodeling may constitute a key mechanism underlying the transition from compensated hypertrophy to HF.

 
 
 
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