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W G Kerrick

Publications and source records attributed to W G Kerrick.

At least 37 records · Page 2Linked to original sources
PubMed1987

MgADP- increases maximum tension and Ca2+ sensitivity in skinned rabbit soleus fibers.

Increasing concentrations of MgADP- or MgCDP- in the millimolar range cause an increase in the maximum Ca2+ -activated tension that a skinned rabbit soleus muscle fiber can develop in the presence of 2 mM MgATP2- or MgCTP2- respectively. In contrast, the maximal Ca2+ -activated ATPase activity of the fiber decreases in the presence of MgADP-. As the nucleoside diphosphate (MgADP- or MgCDP-) concentration is increased, the Ca2+ concentration required for half-maximal activation of tension is reduced. MgADP- has a similar effect on the Ca2+ concentration required to half-maximally activate the fiber ATPase. The effects on tension are due to magnesium nucleoside diphosphate and not some other form of nucleoside diphosphate since the effects occur at both low (pMg 4) and control (pMg 3) Mg2+ concentrations. Cooperativity, as judged by the Hill "n" value relating isometric tension and Ca2+, is less in the presence of 5 mM MgADP- as compared to a control (no added MgADP-) "n" value. Increasing concentrations of inorganic phosphate (Pi) in the millimolar range decrease maximum Ca2+ -activated tension, and increase the concentration of Ca2+ required to half-maximally activate tension, effects opposite to those of MgADP. These data are consistent with the hypothesis that cooperative interactions between actin and myosin can affect the affinity of troponin for Ca2+.

Adenosine Diphosphate↗
PubMed1986

Smooth muscle: regulation by calcium and phosphorylation.

Skinned smooth muscle cell bundles were used to study the mechanisms by which Ca2+ and protein phosphorylation regulate smooth muscle contraction. The sarcolemma of skinned cells is rendered permeable to ions and proteins by chemical treatment, allowing the investigator to control the ionic and protein environment within the cells and to determine the effect of this environment on the activation of contraction and protein phosphorylation. Results from these studies show that there is a strong correlation between myosin light chain phosphorylation and force development in skinned smooth muscle cells. Both protein phosphorylation and the activation of tension are affected in the predicted manner by agents known to affect myosin light chain kinase activity. Phosphorylation or thiophosphorylation of myosin light chains in the absence of Ca2+ is sufficient to fully activate contraction in skinned smooth muscle cells. Subsequent dephosphorylation of the myosin light chains by phosphatase results in muscle relaxation. Activation of contraction in skinned smooth muscle cells requires phosphorylation of myosin light chains by the Ca2+- and calmodulin-dependent myosin light chain kinase.

Animals↗
PubMed1985

Evidence that the Sr2+ activation properties of cardiac troponin C are altered when substituted into skinned skeletal muscle fibers.

Troponin C (TnC) was extracted from skinned skeletal muscle fibers by a method similar to that used previously on myofibrils (Zot, H.G., and Potter, J.D. (1982) J. Biol. Chem. 257, 7678-7683) and replaced with either skeletal (fast-twitch) or cardiac TnC. The relationship between isometric tension and Sr2+ concentration remained essentially the same before removal and after replacement with skeletal or cardiac TnC. Therefore, the origin of the TnC made no difference in the Sr2+ activation properties of the skinned fiber. In contrast, the activation of skinned cardiac fibers is approximately an order of magnitude more sensitive to Sr2+ than skinned skeletal fibers. These results show that the affinity of cardiac TnC for Sr2+ is altered when substituted into skinned skeletal muscle fibers through protein-protein interactions.

Animals↗
PubMed1985

Myosin light chain phosphatase. Effect on the activation and relaxation of gizzard smooth muscle skinned fibers.

Skinned cells of chicken gizzard were used to study the effect of a smooth muscle phosphatase (SMP-IV) on activation and relaxation of tension. SMP-IV has previously been shown to dephosphorylate light chains on myosin. When this phosphatase was added to submaximally Ca2+-activated skinned cells, tension increased while phosphorylation of myosin light chains decreased. In contrast, when the myosin phosphatase was added to cell bundles activated in the absence of Ca2+ by a Ca2+-insensitive myosin light chain kinase, tension and phosphorylation of the myosin light chains both decreased. These data suggest that Ca2+ inhibits the deactivation of tension even when myosin light chains are dephosphorylated to a low level. Furthermore, comparison of Ca2+-activated cells caused to relax in CTP, in the presence or absence of Ca2+, shows that cells in the presence of Ca2+ do not relax completely, whereas in the absence of Ca2+ cells completely relax. Solutions containing Ca2+ and CTP, however, are incapable of generating tension from the resting state. Endogenous myosin light chain kinase is not active in solutions containing CTP and dephosphorylation of myosin light chains occurs in CTP solutions both in the presence and absence of Ca2+. These data imply that Ca2+ inhibits relaxation even though myosin light chains are dephosphorylated. These data are consistent with a model wherein an obligatory Ca2+-activated myosin light chain phosphorylation is followed by a second Ca2+ activation process for further tension development or maintenance.

Animals↗
PubMed1984

Regulation of receptor capping in mouse lymphoma T cells by Ca2+-activated myosin light chain kinase.

Several characteristics of receptor capping in lymphocyte membranes suggest similarities with mechanisms underlying control of contraction in smooth muscle fibers. Both capping and contraction are Ca2+ dependent and require metabolic energy. Contractile proteins such as actin and myosin are associated with the cap, as is calmodulin, which mediates the Ca2+ dependence of smooth muscle contraction. Recent studies have shown that myosin light chain kinase (MLCK), which plays a central role in regulation of smooth muscle contraction, is also present in isolated lymphocyte membrane-cytoskeleton complexes. We have explored this analogy further, using mouse lymphoma T cells whose membranes were rendered permeable to small proteins by using a low-Ca2+ EGTA solution similar to that used to chemically skin smooth muscle cells. Permeabilized lymphocytes were then exposed to solutions containing various combinations of high or low Ca2+, ATP, or other nucleotides (5'-adenylyl imidodiphosphate, adenosine 5'-[gamma-thio]triphosphate, guanosine 5'-[gamma-thio]triphosphate, CTP, ITP, UTP, and GTP), calmodulin, Ca2+-insensitive MLCK (MLCK subunit that has been stripped of the Ca2+ binding site), and the catalytic subunit of cAMP-dependent protein kinase that phosphorylates (and thereby inactivates) MLCK. Capping of concanavalin A-labeled receptors in these various test solutions was scored. In all solutions the capping observed in permeable lymphoma cells correlated well with contraction previously observed in similarly treated skinned smooth muscle fibers, providing strong evidence for the involvement of myosin light chain phosphorylation in the regulation of receptor capping.

Adenosine Triphosphate↗
PubMed1983

Receptor capping in mouse T-lymphoma cells: a Ca2+ and calmodulin-stimulated ATP-dependent process.

The roles that Ca2+, calmodulin, and ATP play in the redistribution of concanavalin A (Con A) binding sites on the surface of mouse T-lymphoma cells were examined. Membranes of cells labeled with fluorescein-conjugated Con A (Fl-Con A) were made permeable ("skinned") to ions and proteins by incubation in a solution containing no added Ca2+, 7 mM EGTA, and ATP. The intracellular ionic and protein concentrations could then be varied, and the degree of Con A receptor capping monitored simultaneously. A graded increase (9.0 to 30%) was found in the number of capped cells with increasing Ca2+ concentration from 10(-6)-10(-4.9) M. Increasing concentrations of trifluoperazine, chlorpromazine, and promethazine (1.5 x 10(-6) to 1.0 x 10(-4) M) in cell suspensions containing 10(-4) M Ca2+ produced graded inhibition of capping in the same order that the drugs bind to calmodulin. Removal of extracellular Ca2+ dissociated (reversed) some of the caps into patches, thus reducing their number (12%). ATP was required for either capping or cap dissociation to occur. Addition of calmodulin (3.9 x 10(-8)-6.3 x 10(-7) M) to the cell suspension increased the Ca2+ sensitivity. These results provide direct evidence that capping of Con A receptors is a reversible process (i) regulated by intracellular Ca2+ concentrations, (ii) requiring ATP as an energy source, and (iii) susceptible to the influence of calmodulin. These findings are consistent with the hypothesis that the collection of surface receptor patches into cap structures is controlled by the interaction of actomyosin filaments, which in turn is regulated by a Ca2+-calmodulin-activated control system.

Adenosine Triphosphate↗
PubMed1983

Gizzard Ca2+-independent myosin light chain kinase: evidence in favor of the phosphorylation theory.

Limited digestion of calmodulin (CaM)-dependent myosin light chain kinase from turkey gizzard with alpha-chymotrypsin in the presence of bound CaM generated an 80,000-dalton kinase fragment that was fully active in the absence of Ca2+. This kinase catalyzed specific Ca2+-independent phosphorylation of the 20,000-dalton light chain of myosin using isolated light chains, intact myosin, and actomyosin. Phosphorylation of myosin in the absence of Ca2+ allowed us to dissociate myosin phosphorylation from other potential Ca2+-dependent regulatory mechanisms, thus permitting an evaluation of the postulated central role of myosin phosphorylation in the regulation of smooth muscle contraction. Ca2+-independent myosin phosphorylation was found to cause loss of Ca2+ sensitivity of 1) actin-activated myosin ATPase activity in a crude actomyosin preparation, and 2) tension development in skinned smooth muscle fibers in the absence of Ca2+. Myosin phosphorylation is, therefore, the key event in actin activation of ATPase activity and initiation of contraction in skinned chicken gizzard fibers.

Actomyosin↗
PubMed1982

Superprecipitation of gizzard actomyosin, and tension in gizzard muscle skinned fibers in the presence of nucleotides other than ATP.

1. Nucleotides which are known to be poor substrates for myosin kinase (ITP, GTP, UTP and CTP) are poor relative to ATP at producing Ca2+-sensitive superprecipitation or tension in smooth-muscle-derived experimental systems. The ability of these nucleotides to support Ca2+-sensitive superprecipitation or tension in striated muscle fibers depends on fiber type, but ranges from poor for GTP to excellent for CTP. 2. Thiophosphate analogs of ITP and GTP (ITP gamma S and GTP gamma S) are poor at irreversibly activating superprecipitation in smooth muscle actomyosin relative to ATP gamma S. 3. [gamma-32P]ITP is poor relative to [gamma-32P]ATP as a substrate of the endogenous myosin light-chain kinase in gizzard actomyosin. 4. The results provide further independent evidence in both gizzard actomyosin and skinned fibers that the smooth muscle Ca2+-control system is based on myosin phosphorylation.

Actomyosin↗
PubMed1982

Phosphorylation-dependent activated tension in skinned gizzard muscle fibers in the absence of Ca2+.

A Ca2+-insensitive myosin light chain kinase was prepared and used in experiments with skinned gizzard fibers. In the absence of Ca2+, this kinase activated isometric force development. The force development was associated with phosphorylation of the 20,000-dalton myosin light chains and addition of Ca2+ did not activate the fibers further. Pretreatment of the fibers with Ca2+-insensitive myosin light chain kinase and adenosine 5'-O-(3-thiotriphosphate) in the absence of Ca2+ caused thiophosphorylation of the light chains and, on the addition of ATP, an activation of isometric tension was observed. The subsequent addition of Ca2+ did not increase force development. A comparison of Ca2+-activated tension in the skinned gizzard muscle fibers with Ca2+-insensitive myosin light chain kinase-activated tension suggests that the phosphorylation of the myosin light chains is the dominant factor in the development of tension in smooth muscle.

Animals↗
PubMed1982

Evidence that myosin light chain phosphorylation regulates contraction in the body wall muscles of the sea cucumber.

The Ca2+ activation mechanism of the longitudinal body wall muscles of Parastichopus californicus (sea cucumber) was studied using skinned muscle fiber bundles. Reversible phosphorylation of the myosin light chains correlated with Ca2+-activated tension and relaxation. Pretreatment of the skinned fibers with AT-P gamma S and high Ca2+ (10(-5)M) resulted in irreversible thiophosphorylation of the myosin light chains and activation of a Ca2+ insensitive tension. In contrast, pretreatment with low Ca2+ (10(-8)M) and ATP gamma S results in no thiophosphorylation of the myosin light chains or irreversible activation of tension. These results are consistent with a Ca2+-sensitive myosin light chain kinase/phosphatase system being responsible for the activation of the muscle. Other agents known to have an effect upon the Ca2+-activated tension in skinned vertebrate smooth muscle fibers (trifluoperazine, catalytic subunit of the cyclic AMP-dependent protein kinase, and calmodulin) did not have an effect on myosin light chain phosphorylation or Ca2+-activated tension. These results suggest a different type of myosin light chain kinase than is found in vertebrate smooth muscle is responsible for the activation of parastichopus longitudinal body wall muscle.

Adenosine Triphosphate↗
PubMed1981

Inhibition of smooth muscle tension by cyclic AMP-dependent protein kinase.

beta-Adrenergic relaxation of smooth muscle by catecholamines has been associated with elevated levels of cyclic AMP. The question arises whether subsequent activation of cyclic AMP-dependent protein kinase has a role in the regulation of smooth muscle contraction. There is substantial evidence that a Ca2+-activated myosin light chain kinase/phosphatase system regulates smooth muscle contraction, and Adelstein et al. have shown that the catalytic subunit of cyclic AMP-dependent protein kinase plays a part in this regulation, by phosphorylation of the high molecular weight subunit of the light chain kinase, which results in a decrease in the activity of the kinase. Here we have shown for the first time that the catalytic subunit of the protein kinase inhibits Ca2+-activated tension in skinned smooth muscle fiber preparations.

Animals↗
PubMed1981

Exogenous calmodulin increases Ca2+ sensitivity of isometric tension activation and myosin phosphorylation in skinned smooth muscle.

We have investigated the effect of exogenous calmodulin on chicken gizzard or rabbit ileum smooth muscle functionally skinned by mechanical grinding or exposure to Triton X-100 detergent. We found that specific protein inhibitor, modulator binding protein, caused a loss of Ca2+-activated tension which was restored by subsequent treatment with calmodulin. Calmodulin at 5 microM increased 10-fold the speed of development of isometric tension while it had no significant effect on the rate of relaxation or on maximum tension at high Ca2+ concentrations. The Ca2+ sensitivity of steady state tension and LC20 phosphorylation were also increased by 5 microM calmodulin. These results are consistent with a calmodulin-regulated light chain kinase/phosphatase system being responsible for activation of tension in smooth muscle.

Animals↗
PubMed1981

Regulation of Ca2+-activated tension in limulus striated muscle.

Skinned tail and leg muscle fibers of the limulus were used to study the mechanism of Ca2+ regulation of contraction. Although a Ca2+-sensitive 31,000 dalton protein phosphorylation could be observed in the presence of [gamma-32P] ATP no such phosphorylation occurred in the presence of [gamma-32P] ITP. Ca2+-activated tension occurred equally as well in ATP and ITP. For this reason we eliminated the possibility that a Ca2+-sensitive myosin light chain kinase/phosphatase system is the mechanism responsible for the Ca2+-activated tension. Other agents known to affect a myosin light chain kinase/phosphatase system showed negative results (ATP gamma S, trifluoperazine, catalytic subunit of the cyclic adenosine 3',5'-monophosphate dependent protein kinase and calmodulin). Troponin I reversibly inhibits Ca2+-activated tension. These results are consistent with thin filament regulation being responsible for Ca2+-activated tension in skinned fibers.

Adenosine Triphosphate↗
PubMed1981

Calcium-regulatory mechanisms. Functional classification using skinned fibers.

The primary purpose of this study was to determine whether various agents (adenosine 3-thiotriphosphate [ATP gamma S], trifluoperazine [TFP], troponin I, the catalytic subunit of the cyclic adenosine 3',5'-monophosphate dependent protein kinase [C-subunit], and calmodulin [CaM]) could be used to classify skinned fiber types, and then to determine whether the proposed mechanisms for Ca2+ regulation were consistent with the results. Agents (ATP gamma S, TFP, C-subunit, CaM) expected to alter a light chain kinase-phosphatase system strongly affect the Ca2+-activated tension in skinned gizzard smooth muscle fibers, whereas these agents have no effect on skinned mammalian striated and scallop adductor fibers. Troponin I, which is known to bind strongly to troponin C and CaM, inhibits Ca2+ activation of skinned mammalian striated and gizzard fibers but not scallop adductor muscle. The results in different types of skinned fibers are consistent with proposed mechanisms for Ca2+ regulation.

Adenosine Triphosphate↗
PubMed1980

Inhibition of Ca2+-activated tension and myosin light chain phosphorylation in skinned smooth muscle strips by the phenothiazines.

The antipsychotic phenothiazine drugs trifluoperazine, chlorpromazine, and promethazine inhibited Ca2+-activated tension in functionally skinned rabbit ileum and rabbit pulmonary artery strips. Exogenous calmodulin rapidly reversed the inhibition of tension. Inhibition of the endogenous myosin light chain kinase by these drugs resulted with ATP or its analog. ATP gamma S, as a substrate. The evidence presented suggests the inhibition of Ca2+ activation of tension in skinned smooth muscle preparations by phenothiazines is due to the inhibition of Ca2+-activated phosphorylation of the 20,000 dalton myosin light chain by the endogenous myosin light chain kinase.

Animals↗