What is the cytoskeleton and its function?

Written by Lorraine V. Espina

Edited and Reviewed by Dr. Reuben J C. Los Baños

What is the cytoskeleton and its function? The cytoskeleton is a complex and changing network of protein filaments and tubules. It exists in the cytoplasm of eukaryotic cells and some prokaryotic cells.

It is a key part of the cell’s structure. It supports the cell and helps with many important functions. The scaffold-like structure supports the cell’s shape. It helps with intracellular transport and cell movement, and it also plays a role in cell division.

Three primary types of filaments make up the cytoskeleton.

1. Microfilaments, also called actin filaments, are the thinnest filaments of the cytoskeleton. Subunits of actin protein compose these.

Cells require microfilaments for various activities:

• maintaining cell shape,
• cell movement, and
• muscle contraction.

Actin filaments are dynamic and may polymerize and depolymerize at a rapid pace to allow the cell to change its shape or move.

2. Intermediate Filaments: These filaments are thicker than microfilaments but thinner than microtubules. In a cell, these give the strength and support needed to handle tension and stress.

Intermediate filaments are stiffer and less dynamic as compared to microfilaments and microtubules. Common examples of intermediate filaments are keratin, vimentin, and desmin. These proteins support various types of cells.

3. Microtubules: These are hollow, cylindrical tubes made up of tubulin protein subunits.

Microtubules take part in numerous processes, which include:

• cell division (mitosis and meiosis),
• intracellular transport, and
• the structural integrity of the cell.

They make up the mitotic spindle during cell division. They also act as a “highway” for motor proteins like kinesins and dyneins, which transport cargo inside the cell.

The functions of the cytoskeleton categorize into several key areas:

• Keep Cell Shape: The cytoskeleton gives the cell a strong framework. This support helps the cell resist deformation when under stress.

• Motor proteins like kinesins and dyneins help move things inside the cell. They travel along microtubules, carrying vesicles, organelles, and other cargo.

• Cell Division: The cytoskeleton helps move chromosomes and split daughter cells in mitosis.

• Cell Motility: The cytoskeleton allows for the movement of the entire cell or parts of the cell. This is important in processes such as tissue development, immune responses, and wound healing.

• Signal Transduction: The cytoskeleton connects with signaling molecules. These molecules influence how cells respond to growth factors and other external signals.

The cytoskeleton is a flexible network. It provides support but also changes and adapts to help the cell meet the demands of its environment.

What is the origin of the cytoskeleton?

The origin of the cytoskeleton has a significant connection to the evolution of cellular life. Most scientists think the cytoskeleton formed early in life’s development on Earth. This likely happened around the same time simple prokaryotic cells, like bacteria, appeared.

The cytoskeleton likely started as a set of proteins. These proteins helped the cell keep its shape and supported movement.

Prokaryotic cells have simpler cytoskeletal elements. They include FtsZ, a protein similar to tubulin that helps with cell division. There’s also MreB, an actin-like protein that supports cell structure.

These ancient elements were much simpler than any eukaryotic cell. They served as the building blocks for more complex cellular systems that followed.

As eukaryotic cells evolved, they became more complex and larger. This growth needed better organization inside the cells. The cytoskeleton developed in these cells. It helps with shape and structure. It also allows the cell to divide, move, and transport materials.

Eukaryotic cells have more complex cytoskeletons than prokaryotes. The various types of filaments found in eukaryotes show what prokaryotes lack.

The evolution of a complex cytoskeleton in eukaryotes likely helped multicellularity arise. This change allowed cells to interact, grow, and take on specific tissue roles.

What can damage the cytoskeleton?

The cytoskeleton is an important structure, but it is susceptible to damage or disruption in several forms. Damage to the cytoskeletal component leads to many varied dysfunctional cellular problems.

The most common reasons leading to cytoskeletal damage include:

1. Mechanical Stress: There is mechanical stress due to the physical forces applied in the surrounding environment of a cell. For example, when tissues deform or cells change shape, the cytoskeleton stretches too much. Its parts can break or become disorganized

• Infectious Agents: Pathogens like viruses, bacteria, and parasites often attack the cytoskeleton. They do this to enter host cells or use the host cell for their needs. .

• Oxidative Stress: Reactive oxygen species come from cellular metabolism or environmental damage. They can harm cytoskeletal proteins.

Oxidative damage can harm cytoskeletal structures. This disruption weakens cell function and stability.

• Genetic Mutations: Changes in genes for cytoskeletal proteins can damage the cytoskeleton. This harms its structure and function. Mutations in the dystrophin gene can cause Duchenne muscular dystrophy.

Dystrophin is a protein that links the cytoskeleton to the cell membrane. This condition weakens muscle cells.

• Nutritional Deficiencies: Missing nutrients like vitamin C can weaken the cytoskeleton. Vitamin C is important in the synthesis of collagen, which supports the cytoskeleton in some tissues. A deficiency will make the cytoskeleton fragile and susceptible to damage.

What happens if the cytoskeleton is defective?

Cytoskeleton defects can harm the cell. They may lead to various functional problems. The various outcomes depend on the specific part that is faulty.

Some common effects of the defective cytoskeleton include the following:

• Loss of Cell Shape and Integrity: The cell might lose its shape, become distorted, or not maintain its structural integrity.

Defective actin filaments can cause cells to become rounded. This change affects their normal shape and can hurt their function.

• Impaired Cell Division: The cytoskeleton helps organize and separate chromosomes when cells divide. Defects in microtubules or the mitotic spindle cause aneuploidy. This means cells have an abnormal number of chromosomes.

It leads to cancer, genetic disorders, or cell death.

• Inability to Move or Migrate: Cells need cytoskeletal components to move. If these parts get damaged, cells can’t move well.

For example, immune cells like macrophages may not be able to move toward infection sites, impairing immune responses.

• Impaired tissue function occurs when cytoskeletal proteins in multicellular organisms malfunction. For example, if muscle fibers fail to contract, they become weak. This can lead to diseases like muscular dystrophy.

• Neurological Diseases: Neurons depend on the cytoskeleton for support. It helps move substances along their long axons.

Mutations in proteins such as tau and neurofilaments connect to neurodegenerative diseases. These include Alzheimer’s disease and Parkinson’s disease.

Which cells lack cytoskeleton?

Most cells have a cytoskeleton. It helps keep their shape. It also supports functions and aids in movement and division. However, there are a few exceptions where certain types of cells lack a cytoskeleton or have a very minimal one:

1. Prokaryotic Cells (Bacteria and Archaea): Prokaryotes, including bacteria and archaea, usually do not have the complex cytoskeleton of eukaryotic cells. They do have simpler proteins that help them maintain their shape and facilitate cellular processes such as division.

The FtsZ protein in bacteria acts like tubulin. It helps prokaryotic cells divide by forming a ring structure, ensuring proper cell division. Protein MreB, similar to actin, aids in keeping the shape of prokaryotic cells.

These structures are simpler than microfilaments, microtubules, and intermediate filaments in eukaryotes. Still, they perform similar basic functions.

• Red blood cells (RBCs) classify as eukaryotic. But they lack most of the usual cytoskeleton found in other cells. Mature RBCs lose their nuclei and most organelles as they mature. They have a small cytoskeleton made of spectrin and actin.

This configuration enables them to maintain their balloonlike biconcave shape. Their incompressibility through tiny capillaries is integral to their need for such a shape.

RBCs are different from other cells. They don’t rely on a complex cytoskeleton for structure or function. Their main job is to transport oxygen.

Most eukaryotic cells rely on their cytoskeleton for survival and function. Prokaryotes have simple cytoskeletal structures too, which help them perform essential cellular tasks.

What are the diseases associated with the cytoskeleton?

Cytoskeletons play a key role in keeping cells shaped, dividing, and transporting materials. When disruptions occur, they can lead to many diseases. A few of the more notable diseases related to defects in the cytoskeleton are:

• Cancer: The cytoskeleton guides cell division. When microtubules, actin, or intermediate filaments have issues, it causes uncontrolled growth. This is a key feature of cancer.

Microtubule abnormalities can cause mistakes in chromosome separation, leading to genetic instability. Mutations in actin and vimentin help cancer cells invade nearby tissues. Drugs like taxanes work on microtubules to stop cancer cell division.

• Muscular Dystrophies: Duchenne muscular dystrophy (DMD) happens when there isn’t enough dystrophin. This protein connects actin filaments to the cell membrane. Without it, muscles weaken and waste away.

This causes trouble walking and can lead to losing mobility. Other muscular dystrophies, like limb-girdle muscular dystrophy, involve similar cytoskeletal protein mutations.

• Neurodegenerative Diseases: Alzheimer’s, Parkinson’s, and ALS (Amyotrophic Lateral Sclerosis) affect the cytoskeleton in neurons. In Alzheimer’s, tau proteins disrupt microtubules, causing cell death.

In Parkinson’s, problems with microtubules hinder the movement of key parts. This is especially true in dopamine-producing neurons.

• Ciliopathies: Primary Ciliary Dyskinesia (PCD) and others result from microtubule defects of cilia. The body compromises respiratory and fertility functions.
• Situs inversus is a condition linked to Kartagener’s syndrome. This syndrome is a form of PCD. In situs inversus, the body mirrors all internal organs.
• Epidermolysis Bullosa (EB) is a skin disorder. It causes fragile skin that develops blisters with little effort. This happens due to a mutation in keratin, which helps stabilize cells.
• Hereditary Spastic Paraplegia (HSP) and Charcot-Marie-Tooth Disease (CMT) are neurodegenerative diseases. They happen due to mutations in proteins like microtubules or neurofilaments in neurons. This leads to muscle weakness, sensory loss, and neuron degeneration.

These defects impact how neurons transport signals. This leads to muscle weakness, sensory loss, and progressive degeneration of motor neurons.

What are some interesting facts about the cytoskeleton?

The cytoskeleton is one of the most interesting and dynamic parts within the cell. Its functions provide support, aid movement, and allow communication within and between cells.

No one matches their complexity. The cytoskeleton is unique because it changes all the time. Most cell structures stay the same. The cell builds and breaks down the cytoskeleton in a continuous cycle.

This will enable the cell to change its shape in a short amount of time, move, and adapt to different conditions. When a cell divides, microtubules change shape.

They form the mitotic spindle. The spindle makes sure the two daughter cells get the same number of chromosomes.

The final feature of the cytoskeleton is intracellular transport. Motor proteins, like kinesin and dynein, act like highways. They transport cargo, such as vesicles and organelles, along microtubules or actin filaments.

This transport process is vital for keeping cells balanced by delivering materials to different cell parts.

In neurons, microtubules serve as tracks. They help transport important components to the synapse. This process can break down in neurodegenerative diseases, such as Alzheimer’s and Parkinson’s.

Notable too are the evolutionary implications of the cytoskeleton. Some scientists believe the cytoskeleton helped eukaryotic cells evolve from prokaryotic ancestors.

Prokaryotes had simple cytoskeletal structures from the start. These helped keep their shape and support cell division.

Eukaryotes later developed a more advanced cytoskeletal network. This change allowed them to grow into larger and more complex organisms.

Conclusion

The cytoskeleton is vital for many functions. It helps maintain cell shape and structure. It also plays a key role in movement, division, and transport.

The cytoskeleton not working can lead to serious problems in many diseases. These diseases affect various tissues and organ systems.

One of the most beautiful things about the cytoskeleton is its ability to adapt. It acts as a flexible framework that meets any new cell needs. So, the shape of the cell changes to fit new parts of the cytoplasm.

This helps with movement and cell division, allowing the cell to grow and thrive. The cytoskeleton helps move things inside the cell.

It carries needed substances along its pathways for the cell to use. These functions show how complex the cytoskeleton is.

They also show its role in the evolution of multicellular systems. The cytoskeleton and its related diseases are important for basic science and clinical medicine.

It sheds light on key cellular processes. This also points to possible treatment targets for various diseases.

The cytoskeleton is more than a simple structure. It is dynamic and serves many functions. It is essential for the health and operation of every cell.

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