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Cardiac myosin is a molecular motor that powers heart contraction by converting chemical energy from ATP hydrolysis into mechanical force. It is a member of the myosin II family, which includes two-headed, filament-forming muscle and non-muscle myosins. Cardiac myosin consists of two heavy chains (MyHC) and two pairs of light chains (MLC). The light chains are arranged in tandem in the head-tail junction, and their function is not yet fully understood. Cardiac myosin is also implicated in muscle regulation, development, and mechanotransduction. Dysfunction of myosin in these processes can lead to a range of cardiac diseases. Recent studies have revealed novel functions and regulatory mechanisms of cardiac myosin, including aging-specific myosin modifications in the rod region of human fast and slow MyHC isoforms. So, does cardiac muscle modify myosin?
| Characteristics | Values |
|---|---|
| Definition | Cardiac myosin is the molecular motor that powers heart contraction. |
| Chemical Energy Conversion | Cardiac myosin converts chemical energy from ATP hydrolysis into mechanical force, leading to the heart's contraction. |
| Structure | Cardiac myosin consists of two heavy chains (MyHC) and two pairs of light chains (MLC). |
| Function | Myosin is the molecular motor that transduces energy from the hydrolysis of adenosine triphosphate (ATP) into directed movement, driving sarcomere shortening and muscle contraction. |
| Types | Cardiac myosin is a member of the myosin II family, which includes two-headed, filament-forming muscle and non-muscle myosins. |
| Modifications | Aging-specific myosin modifications include carbonylations, methylations, and deamidations in the rod region of human fast and slow MyHC isoforms. |
| Role in Disease | Dysfunction of myosin can lead to a range of cardiac diseases with different presentations and prognoses. |
| Antigen | Cardiac myosin is a heart-specific antigen implicated in allograft rejection and autoantibody production. |
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What You'll Learn
- Cardiac myosin is a molecular motor that powers heart contraction
- Cardiac myosin consists of two heavy chains and two pairs of light chains
- Cardiac myosin is implicated in allograft rejection
- Cardiac myosin is a heart-specific protein
- Cardiac myosin is involved in muscle regulation, development, and mechanotransduction
Cardiac myosin is a molecular motor that powers heart contraction
The fundamental contractile unit in cardiac muscle is the sarcomere, which consists of interdigitated thin and thick filaments that lie between α-actinin-containing structures called Z-discs. During muscle contraction, each sarcomere shortens, bringing the Z-discs closer together. This shortening is driven by the sliding of actin and myosin filaments past one another, with the actin filaments moving into the A-band and H-zone. The binding of myosin to actin filaments allows myosin to function as a motor that drives this filament sliding.
Cardiac myosin converts chemical energy from ATP hydrolysis into mechanical force, powering the contraction of the heart. The power output of the heart is tightly regulated to meet the physiological needs of the body. Recent studies have revealed that myosin not only generates power output but also plays an active role in its regulation. For example, cardiac myosin-generated tension affects physiological processes beyond muscle contraction, influencing development and disease.
The expression of myosin isoforms changes over time during development and disease. In a healthy heart, the fraction of MYH7 MHC expressed in the ventricles is typically around 93%. However, in a failing heart, this fraction increases to 100%. Understanding the role of cardiac myosin in health and disease has led to its emergence as a drug target for conditions such as heart failure, with therapeutics aimed at directly tuning myosin contractility.
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Cardiac myosin consists of two heavy chains and two pairs of light chains
Cardiac myosin is a molecular motor that powers heart contraction by converting chemical energy from ATP hydrolysis into mechanical force. It is a member of the myosin II family, which includes two-headed, filament-forming muscle and non-muscle myosins. Cardiac myosin consists of two heavy chains (MyHC) and two pairs of light chains (MLC). The two types of light chains are referred to as essential (or alkali) light chains (MLC-1) and regulatory (or phosphorylatable) light chains (MLC-2). The function of these light chains is not fully understood, but they are believed to modulate the adenosine triphosphatase (ATPase) activity of the myosin head in the presence of actin and contribute to the rigidity of the neck, which may function as a lever arm for generating an effective power stroke.
The myosin molecule is highly asymmetric, with two globular heads joined to a long rod-like tail. The light chains are arranged in tandem in the head-tail junction. Each heavy chain consists of a globular head region and a long α-helical tail. The α-helical tails of the two heavy chains twist around each other in a coiled-coil structure to form a dimer, and two light chains associate with the neck of each head region to form the complete myosin II molecule. The thick filaments of muscle consist of several hundred myosin molecules, which are arranged in a parallel staggered array through interactions between their tails.
The myosin heavy chains and light chains play essential roles in the development and function of the heart. Both types of chains are required for the correct formation of the heart during cardiogenesis. Mutations in the myosin heavy chains and ventricular light chains can lead to congenital heart defects. In addition, the regulatory light chains are involved in the recovery of cardiac muscle function after myocardial infarction.
The contractile elements of the cytoskeleton in cardiac muscle are highly organized arrays that give rise to characteristic patterns of cross-striations. The fundamental contractile unit in cardiac muscle is the sarcomere, which consists of interdigitated thin and thick filaments that lie between α-actinin-containing structures called Z-discs. Myosin is localized to the dark A-band, while the light band that contains actin is called the I-band. Myosin-containing thick filaments are organized into A-bands by myomesin at the M-line and anchored to the Z-discs by titin.
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Cardiac myosin is implicated in allograft rejection
Cardiac myosin is a heart-specific protein that has been identified as a target antigen in murine autoimmune myocarditis. It is implicated in allograft rejection, with pre-transplant myosin autoantibodies correlating with acute cardiac transplant rejection.
Allograft rejection occurs when a transplanted organ or tissue is rejected by the recipient's body. In the context of cardiac myosin, studies have shown that cardiac self-antigen myosin can be the target of a T cell-mediated attack. This means that the recipient's immune system recognizes the transplanted organ as foreign and attacks it, leading to rejection.
Several models of cardiac transplantation in mice and rats suggest that cardiac myosin is recognized by T cells in the context of self-MHC class II molecules on the recipient's antigen-presenting cells. This recognition triggers an immune response that leads to the rejection of the transplanted organ.
Furthermore, studies have shown that sensitization with cardiac myosin before transplantation can lead to accelerated rejection of allogeneic and syngeneic heart grafts. This indicates that the presence of anti-myosin antibodies before transplantation can contribute to the rejection process.
The role of cardiac myosin in allograft rejection is complex and involves various immune and non-immune factors. While immune responses play a predominant role in the rejection process, non-immune factors such as hyperlipidemia, cytomegalovirus infection, and baseline coronary artery disease can also contribute to the development of cardiac allograft vasculopathy, which is a major factor affecting long-term graft and patient survival after heart transplantation.
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Cardiac myosin is a heart-specific protein
Cardiac myosin, a member of the myosin II family, is a heart-specific protein that is found in cardiac muscle cells. It is a molecular motor that powers heart contraction by converting chemical energy from adenosine triphosphate (ATP) hydrolysis into mechanical force, leading to muscle contraction and sarcomere shortening. Cardiac myosin consists of two heavy chains (MyHC) and two pairs of light chains (MLC), specifically two regulatory light chains (RLCs) and two essential light chains (ELCs). The light chains are arranged in tandem in the head-tail junction, and while they are not required for the adenosine triphosphatase (ATPase) activity of the myosin head, they likely modulate it in the presence of actin and contribute to the rigidity of the neck, which functions as a lever arm for generating a power stroke.
Cardiac myosin is biologically active and has been purified from bovine heart muscle for use in F-actin activated ATPase assays. The biological activity of cardiac myosin is determined by its rate of F-actin activated ATP hydrolysis, which is significantly higher in the presence of F-actin. This protein is also being studied in the context of cardiac injury and disease. For example, cardiac myosin has been identified as a target antigen in murine autoimmune myocarditis, and pre-transplant myosin autoantibodies have been correlated with acute cardiac transplant rejection. Furthermore, cardiac myosin-generated tension has been found to affect physiological processes beyond muscle contraction, and its dysfunction can lead to a range of cardiac diseases.
Recent multiscale studies have revealed novel regulatory mechanisms that fine-tune cardiac contraction, showing that myosin is both shaped by and actively involved in shaping its mechanical environment. These findings have led to the emergence of cardiac myosin as a drug target for diseases such as heart failure, with therapeutics being developed to directly tune myosin contractility. Overall, cardiac myosin plays a crucial role in heart contraction and muscle regulation, and its understanding is vital for developing treatments for various cardiac conditions.
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Cardiac myosin is involved in muscle regulation, development, and mechanotransduction
Cardiac myosin is a molecular motor that powers heart contraction by converting chemical energy from ATP hydrolysis into mechanical force. It is a member of the myosin II family, which includes two-headed, filament-forming muscle and non-muscle myosins. Cardiac myosin consists of two heavy chains (MyHC) and two pairs of light chains (MLC). The light chains are arranged in tandem in the head-tail junction, and their function is not yet fully understood.
Cardiac myosin plays a pivotal role in muscle regulation, development, and mechanotransduction. Recent multiscale studies have revealed complex regulatory mechanisms that fine-tune cardiac contraction, showing that myosin is both shaped by and actively involved in shaping its mechanical environment. For example, cardiac myosin-generated tension affects physiological processes beyond muscle contraction, and its dysfunction can lead to a range of cardiac diseases with different presentations and prognoses.
The regulation of cardiac myosin has been a focus of ongoing research, with recent advances made through multiscale studies of increasing complexity and technological innovations. These studies have provided a more nuanced understanding of how the heart fine-tunes its power output over various length and temporal scales. For instance, the speed of muscle contraction has been linked to the length and flexibility of the S2 linker as well as the myosin step size.
Furthermore, cardiac myosin has emerged as a potential drug target for diseases such as heart failure, leading to the development of therapeutics that directly tune myosin contractility. However, there are still many unanswered questions and challenges in this field, especially regarding the structural and biochemical mechanisms by which myosin senses and transduces force. Addressing these questions is crucial for understanding cardiac myosin's physiological role and its contribution to cardiac disease when dysregulated.
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Frequently asked questions
Cardiac myosin is the molecular motor that powers heart contraction by converting chemical energy from ATP hydrolysis into mechanical force. It is a member of the myosin II family, which includes two-headed, filament-forming muscle and non-muscle myosins.
Cardiac myosin is the cytoskeletal motor protein found in cardiac muscle cells, which is directly responsible for converting chemical energy to mechanical force, leading to the heart's contraction.
Cardiac myosin consists of two heavy chains (MyHC) and two pairs of light chains (MLC). The light chains are arranged in tandem in the head-tail junction. The myosin molecule is highly asymmetric, consisting of two globular heads joined to a long rod-like tail.
