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P J Gallagher

Publications and source records attributed to P J Gallagher.

At least 19 recordsLinked to original sources
PubMed1992

Substrate specificity of myosin light chain kinases.

Skeletal muscle myosin light chain kinase can phosphorylate myosin light chains isolated from skeletal or smooth muscle. In contrast, smooth muscle myosin light chain kinase specifically phosphorylates light chains isolated from smooth muscle. In this study, we have identified residues within the rabbit smooth and skeletal muscle myosin light chain kinases which may interact with the basic residues that are important substrate determinants in the light chains. Mutation of aspartic acid 270 amino-terminal of the catalytic core of the skeletal muscle myosin light chain kinase increased the Km value for both smooth and skeletal muscle light chains. Although deletions of the analogous region of the smooth muscle myosin light chain kinase (residues 663-678) markedly increased the Km value for light chain, mutation of any single acidic residue within this region did not have a similar effect. Mutation of single residues within the catalytic core of the skeletal muscle (E377 and E421) and smooth muscle (E777 and E821) myosin light chain kinases increased Km values for the smooth muscle light chain at least 35- and 100-fold, respectively. It is proposed that these residues may form ionic interactions with the arginine that is 3 residues amino-terminal of the phosphorylatable serine in the smooth muscle light chain.

Amino Acid Sequence↗
PubMed1992

Identification of basic residues involved in activation and calmodulin binding of rabbit smooth muscle myosin light chain kinase.

It is postulated that basic residues in the regulatory region of myosin light chain kinase are important for conferring autoinhibition by binding to the catalytic core. To investigate this proposal, 10 basic amino acids within the regulatory region of rabbit smooth muscle myosin light chain kinase (Lys961-Lys979) were replaced either singularly or in combination with acidic or nonpolar residues by site-directed mutagenesis. All active mutant kinases were dependent on Ca2+/calmodulin for catalytic activity. None of the mutants was active in the absence of Ca2+/calmodulin, suggesting that the autoinhibitory region has not been defined completely. Charge reversal mutants at Arg974, Arg975, and Lys976 resulted in loss of high affinity binding of calmodulin and increased the concentration of calmodulin required for half-maximal activation (KCaM). The charge reversal mutant at Lys979 also increased KCaM but to a lesser extent. Charge reversal mutants at Lys965 and Arg967 resulted in an inactive myosin light chain kinase that could not be proteolytically activated. When these residues were mutated to Ala, the expressed kinase was dependent upon Ca2+/calmodulin for activity and exhibited a decrease in KCaM. Charge reversal mutants in Lys961 and Lys962 also had decreased KCaM values. These basic residues amino-terminal of the calmodulin binding domain may play an important role in the activation of the kinase.

Amino Acid Sequence↗
PubMed1992

Biochemical properties of chimeric skeletal and smooth muscle myosin light chain kinases.

The molecular and biochemical properties of myosin light chain kinases from chicken skeletal and smooth muscle were investigated by recombinant DNA techniques. Deletion of the amino-terminal region of either the smooth or skeletal muscle myosin light chain kinase resulted in a decrease in Vmax with no significant change in Km values for light chain substrates. Skeletal/smooth muscle chimeric kinases were inactive when a 65-residue region amino-terminal of the catalytic core was exchanged between the two forms. Changing alanine 494 to glutamic acid within this region in the chicken skeletal muscle myosin light chain kinase increased the Km values for light chains 10-fold. These results are consistent with the hypothesis that the region amino-terminal of the catalytic core in myosin light chain kinases is involved in light chain recognition. A skeletal muscle kinase which contained the smooth muscle calmodulin binding domain remained regulated by Ca2+/calmodulin. Thus, the calmodulin binding domains of smooth and skeletal muscle myosin light chain kinases share structural elements necessary for regulation.

Amino Acid Sequence↗
PubMed1992

Dietary vitamin E and the attenuation of early lesion development in modified Watanabe rabbits.

Modified Watanabe heritable hyperlipidemic rabbits (M-WHHL) were fed either standard rabbit diet or diet supplemented with 0.5% wt/wt of the lipophilic antioxidant vitamin E (d,l-alpha-tocopherol). Animals of 10-12 weeks of age were divided into two groups matched for distribution of serum cholesterol levels at the beginning of the 12 week study period. A significant hypocholesterolemic response to vitamin E feeding was observed throughout the study. Vitamin E supplementation increased serum vitamin E levels approximately fourfold and restricted ex-vivo copper mediated oxidative modification of low density lipoprotein (LDL) as quantitated by fluorescence at 430 nm. Post mortem examination of aortic tissue revealed a significant (32%) inhibition of surface area lesion involvement in the arch region as determined by image analysis. It is concluded that administration of vitamin E to M-WHHL rabbits brings about a significant hypocholesterolemic response, confers on LDL significant protection against oxidative modification and either or both contribute to the inhibition of early aortic lesion development.

Animals↗
PubMed1992

The value of simple morphometric techniques in the diagnosis of osteoporosis.

In order to assess the value of simple morphometric methods in the diagnosis of osteoporosis we measured trabecular bone volume (TBV), trabecular number per unit area and relative osteoid volume in two separate iliac crest biopsies in 20 patients with conclusive autopsy evidence of osteoporosis and 20 controls. In osteoporotic patients trabecular bone volume ranged between 3.0-19.2% (median 10.7%) in the anterior and 3.0-14.3% (median 9.7%) in the posterior biopsy and in controls between 2.5-24.8% (median 13.5%) in the anterior and 5.8-25% (median 12.4%) in the posterior. Trabecular numbers in osteoporotic patients ranged from 1.7-8.3/10 mm2 (median 3.5) and in controls 1.6-17/10 mm2 (median 5.63). Relative osteoid volume showed a similarly wide range. In adjacent biopsies trabecular bone volume and trabecular number could differ by as much as 100% and this casts doubt on the value of sequential bone biopsies in the management of individual patients. We conclude that simple morphometric techniques cannot accurately diagnose osteoporosis. However, if the TBV is greater than 18% osteoporosis is unlikely to be present (upper 95% confidence limit = 17.8%). However, a low value for TBV is not diagnostic for osteoporosis because of a large overlap between control and osteoporotic groups.

Aged↗
PubMed1992

Reduced azole susceptibility of oral isolates of Candida albicans from HIV-positive patients and a derivative exhibiting colony morphology variation.

Approximately 50% (15/28) of a selection of oral isolates of Candida albicans from separate individuals infected with the human immunodeficiency virus (HIV) exhibited low susceptibility to ketoconazole as determined by hyphal elongation assessment. Nine of these isolates exhibited colony morphology variation or switching at 37 degrees C, of which six expressed low ketoconazole susceptibility. To determine whether colony morphology variation could give rise to derivatives with reduced azole susceptibility, several high-frequency switching variants of three HIV-patient isolates were recovered and assessed. All but one of the variants expressed similar azole susceptibility profiles to their respective parental strains. However, the C. albicans derivative 132ACR expressed significantly reduced susceptibility to ketoconazole in comparison to its parental strain 132A. In whole cells, on the basis of total growth the switched derivative 132ACR was markedly less susceptible than its parental isolate 132A to ketoconazole at 10 microM. A much smaller difference was observed with fluconazole at 10 microM, with the switched derivative 132ACR exhibiting a threefold lower susceptibility compared with the parental isolate 132A. The incorporation of [14C]acetate in control and azole-treated cells of both organisms was higher for the parental strain. When cell lysates of strain 132A and its derivative 132ACR were incubated with [14C]mevalonic acid and ketoconazole, the IC50 for 14C-label incorporation into C-4 demethyl sterols was fivefold higher for lysates of the switched derivative 132ACR compared with those of the parental strain 132A. With fluconazole the IC50 value for the derivative 132ACR was 25-fold higher than for strain 132A. The 14-sterol demethylase of the switched derivative 132ACR was possibly less sensitive to azole inhibition than that of the enzyme of strain 132A. These studies indicated that colony morphology variation in vitro can generate derivatives with stable, reduced azole susceptibility without prior exposure to azoles.

Candida albicans↗
PubMed1992

Glycosylation requirements for intracellular transport and function of the hemagglutinin of influenza virus.

The contribution of each of the seven asparagine-linked oligosaccharide side chains on the hemagglutinin of the A/Aichi/68 (X31) strain of influenza virus was assessed with respect to its effect on the folding, intracellular transport, and biological activities of the molecule. Twenty mutant influenza virus hemagglutinins were constructed and expressed, each of which had one or more of the seven glycosylation sites removed. Investigations of these mutant hemagglutinins indicated that (i) no individual oligosaccharide side chain is necessary or sufficient for the folding, intracellular transport, or function of the molecule, (ii) at least five oligosaccharide side chains are required for the X31 hemagglutinin molecule to move along the exocytic pathway to the plasma membrane, and (iii) mutant hemagglutinins having less than five oligosaccharide side chains form intracellular aggregates and are retained in the endoplasmic reticulum.

Amino Acid Sequence↗
PubMed1992

Raised blood urea in the elderly: a clinical and pathological study.

We have attempted to define a normal range for blood urea and creatinine for elderly inpatients and to determine the relative importance of pre-renal, renal and post-renal pathology in those with renal impairment. A total of 118 admissions to an acute geriatric unit and 67 separate post mortems in patients over 67 years of age were studied prospectively. Up to 123 items of data were coded and analysed including blood urea and creatinine, clinical or pathological changes associated with renal disease, clinical outcome and post mortem findings. We determined our own 'normal' hospital ranges for urea (1.4-13.2 mmol/l) and creatinine (48-141 mumol/l) from plasma values in 76 patients with no evidence of renal impairment, either on admission or in the past. Using these values 41% of post mortem cases and 25% of clinical admissions had a raised blood urea. Pre-renal conditions such as cardiac failure, dehydration and gastrointestinal haemorrhage, either alone or in combination, were present in 56% of these patients. Urea and creatinine values were substantially higher in patients who died in hospital as opposed to those who were discharged or transferred. Creatinine values were greater in those with intrinsic renal disease or post-renal obstruction as compared to patients with pre-renal causes of renal impairment. Patients with histological evidence of extensive glomerulosclerosis or nephrosclerosis had higher urea and creatinine levels than those with only minor ageing changes.

Aged↗
PubMed1992

Local audit of surgical pathology. 18 month's experience of peer review-based quality assessment in an English teaching hospital.

In order to assess the performance of a surgical pathology laboratory in a university hospital, we have established a comprehensive system of quality audit based on peer review. Each month, 2% of cases received are selected at random and assessed retrospectively by two senior pathologists. The system, which uses semi-quantitative scoring, examines diagnostic accuracy, identifies delay at any stage in the production of reports, evaluates the overall quality of the slides, the presentation of the final report, and the accuracy of the SNOMED coding. Each of these parameters is graded as "satisfactory," "borderline," or "unsatisfactory." In 20 of 518 cases (3.9%) analyzed in 18 months, the microscopic report was unsatisfactory; in six of these cases, the error could have affected patient management. Remediable faults were detected in the macroscopic description of specimens and in the speed and accuracy of report typing by the secretarial staff. In 13 of 18 months, greater than 10% of reports were delayed because of the time taken in microscopic reporting by pathologists. Some (but not all) of this delay was attributable to the "checking out" of pathologists in training. We conclude that this audit system has uncovered substantial deficiencies in our departmental performance, some of which could affect the clinical course of patients. These surprising results suggest that a system of peer review should be adopted more widely.

England↗
PubMed1991

Molecular characterization of a mammalian smooth muscle myosin light chain kinase.

A 5.6-kilobase cDNA clone has been isolated which includes the entire coding region for the myosin light chain kinase from rabbit uterine tissue. This cDNA, expressed in COS cells, encodes a Ca2+/calmodulin-dependent protein kinase with catalytic properties similar to other purified smooth muscle myosin light chain kinases. A module (TLKPVGNIKPAE), repeated sequentially 15 times, has been identified near the N terminus of this smooth muscle kinase. It is not present in chicken gizzard or rabbit skeletal muscle myosin light chain kinases. This repeat module and a subrepeat (K P A/V) are similar in amino acid content to repeated motifs present in other proteins, some of which have been shown to associate with chromatin structures. Immunoblot analysis after sodium dodecyl sulfate-polyacrylamide gel electrophoresis, used to compare myosin light chain kinase present in rabbit, bovine, and chicken smooth and nonmuscle tissues, showed that within each species both tissue types have myosin light chain kinases with indistinguishable molecular masses. These data suggest that myosin light chain kinases present in smooth and nonmuscle tissues are the same protein.

Amino Acid Sequence↗
PubMed1991

The carboxyl terminus of the smooth muscle myosin light chain kinase is expressed as an independent protein, telokin.

It has been proposed that the carboxyl terminus of the smooth muscle myosin light chain kinase is expressed as an independent protein. This protein has been purified from tissues and named telokin (Ito, M., Dabrowska, R., Guerriero, V., Jr., and Hartshorne, D. J. (1989) J. Biol. Chem. 264, 13971-13974). In this study we have isolated and characterized cDNA and genomic clones encoding telokin. Analysis of a genomic DNA clone suggests that the mRNA encoding telokin arises from a promoter which appears to be located within an intron of the smooth muscle myosin light chain kinase (MLCK) gene. This intron interrupts exons encoding the calmodulin binding domain of the kinase. The amino acid sequence deduced from the cDNA predicts that telokin is identical to the carboxyl-terminal 155 residues of the smooth muscle MLCK. Unlike the smooth muscle MLCK which is expressed in both smooth and non-muscle tissues, telokin is expressed in some smooth muscle tissues but has not been detected in aortic smooth muscle or in any non-muscle tissues.

Amino Acid Sequence↗
PubMed1991

Surgical pathology of cranial arteritis and polymyalgia rheumatica.

In both clinical and histological terms cranial arteritis is one of the most distinctive of all vascular disorders. The dense granulomatous inflammatory infiltrates which characterize the acute stages of the disease resemble those of Takayasu's arteritis or granulomatous angiitis of the central nervous system, but the clinicopathological features in patients with positive temporal artery biopsies are diagnostic. Well over a third of patients with classical signs and symptoms of cranial arteritis have negative temporal artery biopsies, and focal involvement of arteries of the head and neck is the probable explanation for this. Pathologists should be aware of the wide spectrum of histological changes that occur in muscular arteries as part of normal ageing and must not interpret these as evidence of healed arteritis. The histological changes of healed arteritis include medial chronic inflammation with ingrowth of new blood vessels, focal medial scarring and a bizarre pattern of intimal fibrosis. Although ultrastructural and immunohistochemical studies have provided some insight into the underlying pathological changes, they have not contributed directly to the diagnosis of cranial arteritis. Between 15 and 55% of patients with polymyalgia rheumatica have positive temporal artery biopsies, but apart from an elevated ESR there are no other laboratory investigations or biopsy procedures that contribute to diagnosis.

Arteries↗
PubMed1991

Vascular smooth muscle contractile elements. Cellular regulation.

For many years the simple view was held that contractile force in smooth muscle was proportional to cytosolic Ca2+ concentrations ([Ca2+]i). With the discovery that phosphorylation of myosin light chain by Ca2+/calmodulin-dependent myosin light chain kinase initiated contraction, regulation of the contractile elements developed more complex properties. Molecular and biochemical investigations have identified important domains of myosin light chain kinase: light chain binding sites, catalytic core, pseudosubstrate prototope, and calmodulin-binding domain. New protein phosphatase inhibitors such as okadaic acid and calyculin A should help in the identification of the physiologically important phosphatase and potential modes of regulation. The proposal of an attached, dephosphorylated myosin cross bridge (latch bridge) that can maintain force has evoked considerable controversy about the detailed functions of the myosin phosphorylation system. The latch bridge has been defined by a model based on physiological properties but has not been identified biochemically. Thin-filament proteins have been proposed as secondary sites of regulation of contractile elements, but additional studies are needed to establish physiological roles. Changes in the Ca2+ sensitivity of smooth muscle contractile elements with different modes of cellular stimulation may be related to inactivation of myosin light chain kinase or activation of protein phosphatase activities. Thus, contractile elements in smooth muscle cells are not dependent solely on [Ca2+]i but use additional regulatory mechanisms. The immediate challenge is to define their relative importance and to describe molecular-biochemical properties that provide insights into proposed physiological functions.

Amino Acid Sequence↗
PubMed1990

Acidic residues comprise part of the myosin light chain-binding site on skeletal muscle myosin light chain kinase.

Myosin light chain kinase is a Ca2+/calmodulin-dependent protein kinase which exhibits a very high degree of protein substrate specificity. The regulatory light chain of myosin is the only known physiological substrate of the enzyme. Based upon epitope mapping of monoclonal antibodies which inhibit kinase activity competitively with respect to the light chain substrate, residues 235-319 of the rabbit skeletal muscle kinase have been proposed to contain a light chain-binding site (Herring, B. P., Stull, J. T., and Gallagher, P. J. (1990) J. Biol. Chem. 265, 1724-1730). With the expression of a truncated kinase, we have further localized this putative binding site to residues 235-294. Mutation of acidic residues at positions 269 and 270 of the kinase resulted in a 10-fold increase in the Km value for the myosin light chain, with no significant change in the Vmax value. In contrast, altering a cluster of acidic amino acids at positions 261-263 had little effect on the Km value for the myosin light chain. These results suggest that residues 269 and 270 may be involved in protein-substrate binding. Interestingly, these residues, located amino-terminal of the homologous catalytic core (positions 302-539), are in a region which is highly conserved among myosin light chain kinases, but not other protein kinases. It is probable that the homologous catalytic core contains structural elements required for phosphotransferase activity. The catalytic domain of myosin light chain kinase would therefore include these conserved elements together with additional specific substrate-binding residues.

Amino Acid Sequence↗