scholarly journals X-ROS Signaling Depends on Length-Dependent Calcium Buffering by Troponin

Cells ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 1189
Author(s):  
Sarita Limbu ◽  
Benjamin L. Prosser ◽  
William J. Lederer ◽  
Christopher W. Ward ◽  
Mohsin S. Jafri
Keyword(s):  
Calcium Binding ◽  
Calcium Release ◽  
Calcium Transient ◽  
Troponin C ◽  
Buffering Capacity ◽  
Oxygen Species ◽  
Open Probability ◽  
Ros Signaling ◽  
Calcium Buffering ◽  
Calcium Affinity

The stretching of a cardiomyocyte leads to the increased production of reactive oxygen species that increases ryanodine receptor open probability through a process termed X-ROS signaling. The stretching of the myocyte also increases the calcium affinity of myofilament Troponin C, which increases its calcium buffering capacity. Here, an integrative experimental and modeling study is pursued to explain the interplay of length-dependent changes in calcium buffering by troponin and stretch-activated X-ROS calcium signaling. Using this combination, we show that the troponin C-dependent increase in myoplasmic calcium buffering during myocyte stretching largely offsets the X-ROS-dependent increase in calcium release from the sarcoplasmic reticulum. The combination of modeling and experiment are further informed by the elimination of length-dependent changes to troponin C calcium binding in the presence of blebbistatin. Here, the model suggests that it is the X-ROS signaling-dependent Ca2+ release increase that serves to maintain free myoplasmic calcium concentrations during a change in myocyte length. Together, our experimental and modeling approaches have further defined the relative contributions of X-ROS signaling and the length-dependent calcium buffering by troponin in shaping the myoplasmic calcium transient.

scholarly journals Stretch of active muscle during the declining phase of the calcium transient produces biphasic changes in calcium binding to the activating sites.

1990 ◽  
Vol 96 (5) ◽  
pp. 1013-1035 ◽  
Author(s):  
A M Gordon ◽  
E B Ridgway
Keyword(s):  
Calcium Binding ◽  
Time Course ◽  
Control Level ◽  
Calcium Transient ◽  
Length Change ◽  
Positive Phase ◽  
Active Force ◽  
Cross Bridge ◽  
Calcium Affinity ◽  
Cross Bridges

In voltage-clamped barnacle single muscle fibers, muscle shortening during the declining phase of the calcium transient increases myoplasmic calcium. This extra calcium is probably released from the activating sites by a change in affinity when cross-bridges break (Gordon, A. M., and E. B. Ridgway, 1987. J. Gen. Physiol. 90:321-340). Stretching the muscle at similar times causes a more complex response, a rapid increase in intracellular calcium followed by a transient decrease. The amplitudes of both phases increase with the rate and amplitude of stretch. The rapid increase, however, appears only when the muscle is stretched more than approximately 0.4%. This is above the length change that produces the breakpoint in the force record during a ramp stretch. This positive phase in response to large stretches is similar to that seen on equivalent shortening at the same point in the contraction. For stretches at different times during the calcium transient, the peak amplitude of the positive phase has a time course that is delayed relative to the calcium transient, while the peak decrease during the negative phase has an earlier time course that is more similar to the calcium transient. The amplitudes of both phases increase with increasing strength of stimulation and consequent force. When the initial muscle the active force. A large decrease in length (which drops the active force to zero) decreases the extra calcium seen on a subsequent restretch. After such a shortening step, the extra calcium on stretch recovers (50 ms half time) toward the control level with the same time course as the redeveloped force. Conversely, stretching an active fiber decreases the extra calcium on a subsequent shortening step that is imposed shortly afterward. Enhanced calcium binding due to increased length alone cannot explain our data. We hypothesize that the calcium affinity of the activating sites increases with cross-bridge attachment and further with cross-bridge strain. This accounts for the biphasic response to stretch as follows: cross-bridges detached by stretch first decrease calcium affinity, then upon reattachment increase calcium affinity due to the strained configuration brought on by the stretch. The experiments suggest that cross-bridge attachment and strain can modify calcium binding to the activating sites in intact muscle.

Calcium binding proteins. Elucidating the contributions to calcium affinity from an analysis of species variants and peptide fragments

1990 ◽  
Vol 68 (3) ◽  
pp. 587-601 ◽  
Author(s):  
Brian J. Marsden ◽  
Gary S. Shaw ◽  
Brian D. Sykes
Keyword(s):  
Binding Affinity ◽  
Sequence Homology ◽  
Calcium Binding ◽  
Binding Proteins ◽  
Troponin C ◽  
Calcium Binding Proteins ◽  
Intact Protein ◽  
Peptide Fragments ◽  
Helix Loop Helix ◽  
Calcium Affinity

This paper describes the sequence homology of calcium-binding proteins belonging to the troponin C superfamily. Specifically, this similarity has been examined for 276 twelve-residue calcium-binding loops. It has been found that, in the calcium-binding loop, several residues appear invariant, regardless of the species of origin or the affinity of the protein. These residues are Asp at position 1 (+ X of the coordinating position of the calcium), Asp or Asn at position 3 (+ Y), Gly at position 6, Ile at position 8, and Glu at position 12 (− Z). It has also been found that conservation of certain residues can vary in similar sites in similar proteins. For example, position 3 (+ Y) in site 3 of troponin C is always an Asn, whereas in calmodulin the residue is always Asp. This study also examined the calcium-binding affinities of peptide fragments comprising the loop, helix–loop, loop–helix, and helix–loop–helix. These were compared with larger enzymatic or chemically generated protein fragments in an effort to understand the various contributions to the calcium-binding affinity of a single-site versus a two-site domain as found in troponin C and calmodulin. Based on free energy differences, it was found that a 34-residue helix–loop–helix peptide represents about 60% of the binding affinity found in the intact protein. Cooperativity with a second calcium binding site accounted for the remaining 40% of the affinity.Key words: calcium-binding proteins, sequence homology, peptide fragments, species variants, calcium affinity.

scholarly journals Crystallization of a synthetic analog of calcium-binding site III of rabbit skeletal troponin C

1989 ◽  
Vol 264 (17) ◽  
pp. 10261-10263
Author(s):  
L T J Delbaere ◽  
M Vandonselaar ◽  
R E Reid
Keyword(s):  
Binding Site ◽  
Calcium Binding ◽  
Troponin C ◽  
Synthetic Analog ◽  
Calcium Binding Site

scholarly journals Mutation of the high affinity calcium binding sites in cardiac troponin C.

1992 ◽  
Vol 267 (2) ◽  
pp. 825-831 ◽  
Author(s):  
J C Negele ◽  
D G Dotson ◽  
W Liu ◽  
H L Sweeney ◽  
J A Putkey
Keyword(s):  
Binding Sites ◽  
Calcium Binding ◽  
Cardiac Troponin ◽  
Troponin C ◽  
High Affinity ◽  
Cardiac Troponin C ◽  
Calcium Binding Sites

The amino acid sequence of porcine intestinal calcium-binding protein

1979 ◽  
Vol 57 (6) ◽  
pp. 737-748 ◽  
Author(s):  
Theo Hofmann ◽  
Michiko Kawakami ◽  
Anthony J. W. Hitchman ◽  
Joan E. Harrison ◽  
Keith J. Dorrington
Keyword(s):  
Mass Spectrometry ◽  
Amino Acid ◽  
Amino Acid Sequence ◽  
Intestinal Mucosa ◽  
Calcium Binding ◽  
Binding Protein ◽  
Troponin C ◽  
Calcium Binding Protein ◽  
Mass Spectrometry Analysis ◽  
Spectrometry Analysis

The complete amino acid sequence of the calcium-binding protein (CaBP) from pig intestinal mucosa has been determined: Ac-Ser-Ala-Gln-Lys-Ser-Pro-Ala-Glu-Leu-Lys-Ser-Ile-Phe-Glu-Lys-Tyr-Ala-Ala-Lys-Glu-Gly-Asp-Pro-Asn-Gln-Leu-Ser-Lys-Glu-Glu-Leu-Lys-Gln-Leu-Ile-Gln-Ala-Glu-Phe-Pro-Ser-Leu-Leu-Lys-Gly-Pro-Arg-Thr-Leu-Asp-Asp-Leu-Phe-Gln-Glu-Leu-Asp-Lys-Asn-Gly-Asn-Gly-Glu-Val-Ser-Phe-Glu-Glu-Phe-Gln-Val-Leu-Val-Lys-Lys-Ile-Ser-Gln-OH. The N-terminal octapeptide sequence was determined by mass spectrometry analysis by Morris and Dell. The first 45 residues of bovine CaBP differ only in six positions from the corresponding sequence of the porcine protein, except that the sequence starts in position two of the porcine sequence. The mammalian intestinal CaBP's belong to the troponin-C superfamily on the basis of an analysis by Barker and Dayhoff.

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