PubMed Health⌕ Search

Biomedical subjects

Michael P Czubryt

Publications and source records attributed to Michael P Czubryt.

8 recordsLinked to original sources
PubMed2006

RanGAP-mediated nuclear protein import in vascular smooth muscle cells is augmented by lysophosphatidylcholine.

The intracellular mechanism responsible for the mitogenic effects of lysophosphatidylcholine (LPC) is unclear. Import of proteins from the cytoplasm into the cell nucleus is integral to the regulation of gene expression and cell growth. We hypothesized that LPC exerts its intracellular effects through alterations in nuclear protein import. Rabbit aortic smooth muscle cells incubated with LPC induced a significant increase in cell proliferation in both quiescent cells (63.2+/-6.48% of control) and cells grown in 1% fetal bovine serum (FBS) (28.3+/-7.35% of control). Vascular smooth muscle cells were preincubated with LPC then microinjected with a marker protein for nuclear import. A significant stimulation of nuclear protein transport was observed. Using a conventional nuclear protein import assay in permeabilized cells, a significant stimulation of import (72.3+/-5.2% of control) was again observed when the cytosolic nuclear import cocktail was treated with LPC. This effect was not observed with other lysophosphatidyl species. LPC also activated the extracellular signal-regulated kinase (ERK) 1/2 mitogen-activated protein kinase (MAPK) pathway, and this was blocked by 2'-amino-3'-methoxyflavone (PD98059), which inhibits the activation of ERK 1/2. The stimulation of nuclear import was also blocked by PD98059. LPC-induced MAPK activation augmented GTP hydrolysis by RanGAP, a RanGTPase activating protein and a critical regulatory component of nuclear protein import, and this stimulation was again blocked by PD98059. We conclude that LPC alters gene expression and cell proliferation through striking effects on nuclear protein import via a MAP kinase-induced activation of RanGAP. This may play an important role in cancer and atherosclerosis and other disorders involving accelerated cell growth/proliferation.

Active Transport, Cell Nucleus↗
PubMed2006

The role of sex in cardiac function and disease.

In the past decade, increasing attention has been paid to the importance of sex in the etiology of cardiac dysfunction. While focus has been primarily on how sex modulates atherogenesis, it is becoming clear that sex is both a predictor of outcome and an independent risk factor for a number of other cardiac diseases. Animal models and human studies have begun to shed light on the mechanisms by which sex influences the function of cardiomyocytes in health and disease. This review will survey the current literature on cardiac diseases that are influenced by sex and discuss the intracellular mechanisms by which steroid sex hormones affect heart function. A theory on how sex may regulate myocardial energy metabolism to affect disease susceptibility and progression will be presented, as well as a discussion of how sex may influence outcomes of experiments on isolated cardiomyocytes by epigenetic marking.

Androgens↗
PubMed2005

Requirement for serum response factor for skeletal muscle growth and maturation revealed by tissue-specific gene deletion in mice.

Serum response factor (SRF) controls the transcription of muscle genes by recruiting a variety of partner proteins, including members of the myocardin family of transcriptional coactivators. Mice lacking SRF fail to form mesoderm and die before gastrulation, precluding an analysis of the roles of SRF in muscle tissues. To investigate the functions of SRF in skeletal muscle development, we conditionally deleted the Srf gene in mice by skeletal muscle-specific expression of Cre recombinase. In mice lacking skeletal muscle SRF expression, muscle fibers formed, but failed to undergo hypertrophic growth after birth. Consequently, mutant mice died during the perinatal period from severe skeletal muscle hypoplasia. The myopathic phenotype of these mutant mice resembled that of mice expressing a dominant negative mutant of a myocardin family member in skeletal muscle. These findings reveal an essential role for the partnership of SRF and myocardin-related transcription factors in the control of skeletal muscle growth and maturation in vivo.

Animals↗
PubMed2005

Calcineurin is necessary for the maintenance but not embryonic development of slow muscle fibers.

Skeletal muscles are a mosaic of slow and fast twitch myofibers. During embryogenesis, patterns of fiber type composition are initiated that change postnatally to meet physiological demand. To examine the role of the protein phosphatase calcineurin in the initiation and maintenance of muscle fiber types, we used a "Flox-ON" approach to obtain muscle-specific overexpression of the modulatory calcineurin-interacting protein 1 (MCIP1/DSCR1), an inhibitor of calcineurin. Myo-Cre transgenic mice with early skeletal muscle-specific expression of Cre recombinase were used to activate the Flox-MCIP1 transgene. Contractile components unique to type 1 slow fibers were absent from skeletal muscle of adult Myo-Cre/Flox-MCIP1 mice, whereas oxidative capacity, myoglobin content, and mitochondrial abundance were unaltered. The soleus muscles of Myo-Cre/Flox-MCIP1 mice fatigued more rapidly than the wild type as a consequence of the replacement of the slow myosin heavy chain MyHC-1 with a fast isoform, MyHC-2A. MyHC-1 expression in Myo-Cre/Flox-MCIP1 embryos and early neonates was normal. These results demonstrate that developmental patterning of slow fibers is independent of calcineurin, while the maintenance of the slow-fiber phenotype in the adult requires calcineurin activity.

Animals↗
PubMed2004

Balancing contractility and energy production: the role of myocyte enhancer factor 2 (MEF2) in cardiac hypertrophy.

Cardiac hypertrophy -- that is, enlargement of the heart resulting from increased myocyte size -- is observed with many forms of human heart disease. It may arise secondary to an insult, such as infarct or chronic hypertension, or may occur as a consequence of a genetic defect, such as in hypertrophic cardiomyopathy. Traditionally, it has been widely believed that hypertrophy occurred as an adaptive response to normalize increased wall stress due to disease. Recently, however, it has been observed that while hypertrophy initially appears to improve the function of the heart following insult, over time, it frequently leads to a decompensated state, characterized by fibrosis and chamber dilation, resulting in overt heart failure. Hypertrophy also occurs during fetal development, immediately after birth, and in trained athletes; however, it does not lead to decompensation in these states. Experiments over the last 15 years have implicated similar signaling pathways in both pathological and physiological hypertrophic responses. Recently, important differences have been demonstrated that might hold the key to the development of effective new treatments for human diseases. This chapter focuses on how these hypertrophic responses differ from one another phenotypically and discusses how inefficient or impaired energy metabolism in the heart may contribute to the development of pathological responses. We also discuss recent evidence that the myocyte enhancer factor 2 (MEF2) transcription factor family, which previously has been shown to be important in cardiac development and hypertrophy, may have a role in regulation of cardiac energy metabolism.

Animals↗
PubMed2003

Regulation of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1 alpha ) and mitochondrial function by MEF2 and HDAC5.

The myocyte enhancer factor-2 (MEF2) transcription factor regulates muscle development and calcium-dependent gene expression. MEF2 activity is repressed by class II histone deacetylases (HDACs), which dissociate from MEF2 when phosphorylated on two serine residues in response to calcium signaling. To explore the potential importance of MEF2/HDAC interactions in the heart, we generated transgenic mice expressing a signal-resistant form of HDAC5 under cardiac-specific and doxycycline-inducible regulation. Transgene expression resulted in sudden death in male mice accompanied by loss and morphologic changes of cardiac mitochondria and down-regulation of mitochondrial enzymes. The transcriptional coactivator PGC-1 alpha, a master regulator of mitochondrial biogenesis and fatty acid oxidation, was also down-regulated in response to HDAC5 expression. Examination of the PGC-1 alpha promoter revealed two MEF2-binding sites that mediate transcriptional activation by MEF2 and repression by HDAC5. These findings identify PGC-1 alpha as a key target of the MEF2/HDAC regulatory pathway and demonstrate this pathway's importance in maintenance of cardiac mitochondrial function.

Acetylation↗
PubMed2002

Nucleolin is a calcium-binding protein.

We have purified a prominent 110-kDa protein (p110) from 1.6 M NaCl extracts of rat liver nuclei that appears to bind Ca2+. p110 was originally identified by prominent blue staining with 'Stains-All' in sodium dodecyl sulfate-polyacrylamide gels and was observed to specifically bind ruthenium red and 45Ca2+ in nitrocellulose blot overlays. In spin-dialysis studies, purified p110 saturably bound approximately 75 nmol Ca2+/mg protein at a concentration of 1 mM total Ca2+ with half-maximal binding observed at 105 microM Ca2+. With purification, p110 became increasingly susceptible to proteolytic (likely autolytic) fragmentation, although most intermediary peptides between 40 and 90 kDa retained "Stains-All", ruthenium red, and 45Ca2+ binding. N-terminal sequencing of intact p110 and a 70-kDa autolytic peptide fragment revealed a strong homology to nucleolin. Two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)/IEF revealed autolysis produced increasingly acidic peptide fragments ranging in apparent pI's from 5.5 for intact p110 to 3.5 for a 40 kDa peptide fragment. Intact p110 and several peptide fragments were immunostained with a highly specific anti-nucleolin antibody, R2D2, thus confirming the identity of this protein with nucleolin. These annexin-like Ca2+-binding characteristics of nucleolin are likely contributed by its highly acidic argyrophilic N-terminus with autolysis apparently resulting in largely selective removal of its basic C-terminal domain. Although the Ca2+-dependent functions of nucleolin are unknown, we discuss the possibility that like the structurally analogous HMG-1, its Ca2+-dependent actions may regulate chromatin structure, possibly during apoptosis.

Animals↗