Name: actin filaments in cell movement
Uploaded: 2023-04-30T10:16:47.000Z
Duration: 1 min 13 s
Channel: JoVE

Cells must follow environmental cues and rearrange their internal components to migrate from one location to another.
This is primarily achieved through actin-filament reorganization at the cell&#39;s leading edge.
Actin is a multi-functional, globular protein that can polymerize to form polarized F-actin filaments with two distinguished ends &#8211; plus and minus.
They form a tough and flexible framework that supports and strengthens the cell membrane.
In response to appropriate signals, the actin monomers start assembling at the plus ends or branching at sides of existing filaments.
Simultaneously, the minus ends depolymerize and sever, releasing actin monomers that can be recycled back to the polymerizing end.
The continuous force generated by the directional polymerization of the actin filaments pushes the membrane outwards, forming membrane protrusions.
These protrusions help the cell to adhere to the matrix, sense their immediate environment, and allow forward cell displacement by retraction.

actin polymerization and cell motility

Actin Polymerization and Cell Motility

Actin is a family of globular proteins that are highly abundant in eukaryotic cells. It makes up approximately 1-5% of total cell protein concentration. Actin monomers polymerize to form a complex network of polarized filaments, the actin cytoskeleton, that plays a crucial role in many cellular processes, including cell motility, division, endocytosis, and metastasis of cancer cells.
Actin cytoskeleton dynamics can produce pushing, pulling, and resistance forces that help the cell to migrate. This is achieved by forming different types of membrane protrusions, depending on the cell type and the extracellular signals. Primarily, cells move by recurrent cycles of protrusion and attachment of the cell front to the substratum, followed by detachment and retraction at their rear end.
The human genome encodes six highly conserved actin proteins&#8212;ACTC1, ACTA1, ACTA2, ACTG1, ACTG2, and ACTB; all expressed in different cell types. Mutations in any of these six actin genes or the genes encoding actin-binding proteins can lead to disease. For example, mutations in the ACTA1 gene can lead to muscle weakness, especially in the respiratory muscles, which can cause breathing difficulties &#8212; a condition called Nemaline Myopathy. Similarly, mutations in the WAS gene, a key regulator of actin filament nucleation, which is important for cell adhesion, chemotaxis, and phagocytosis of immune cells, causes Wiskott Aldrich syndrome in humans.

Actin is a family of globular proteins that are highly abundant in eukaryotic cells. It makes up approximately 1-5% of total cell protein concentration. ...

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JoVE Core

Cell Biology

Unit 1

Cell Polarization and Migration

KEY TERMS AND CONCEPTS

actin filaments in cell movement

Actin filaments help cells move, divide, and take in material from outside the cell. Actin is a family of globular proteins that is very abundant in eukaryotic cells. It makes up about 1 to 5 percent of total cell protein concentration.

Actin monomers can join together to form a polarized network called the actin cytoskeleton. This network creates pushing, pulling, and resistance forces that support cell migration. Cell movement often follows repeated steps of front-edge protrusion, attachment to the surface, rear-end detachment, and retraction.

The actin system can form different membrane protrusions depending on the cell type and outside signals. The human genome encodes six highly conserved actin proteins: ACTC1, ACTA1, ACTA2, ACTG1, ACTG2, and ACTB. These actins are expressed in different cell types, and mutations in any of these actin genes or in genes for actin-binding proteins can lead to disease.

One example is ACTA1 mutations, which can cause Nemaline Myopathy. This condition can lead to muscle weakness, especially in the respiratory muscles, and may cause breathing difficulties. Another example is the WAS gene, which helps control actin filament nucleation, a step important for cell adhesion, chemotaxis, and phagocytosis in immune cells. WAS mutations cause Wiskott Aldrich syndrome in humans.

Actin Filaments in Cell Movement

cell migration

Cell Migration in Wound Healing and Cancer

Cell migration is the movement of cells from one place to another. It is important in embryological development, repair and regeneration, immune response, and metastasis. Cells respond to chemical signals or mechanical signals from specific organs or tissues. The movement process has three main steps: polarization, protrusion, and release. During polarization, the cell forms a clear front and rear, which sets the direction of movement. Then the front protrudes, forms new adhesions, and creates...

Actin filaments help cells move, divide, and take in material from outside the cell. Actin is a family of globular proteins that is very abundant in eukaryotic cells. It makes up about 1 to 5 percent of total cell protein concentration. Actin monomers can join together to form a polarized network called the actin cytoskeleton. This network creates pushing, pulling, and resistance forces that support cell migration. Cell movement often follows repeated steps of front-edge protrusion, attachment...

types of membrane protrusions

Cell Surface Protrusions in Movement

Cell surface protrusions help cells move, absorb nutrients, and respond to their surroundings. These extensions form when the cytoskeleton, the cell’s internal support system, rearranges. The most commonly seen protrusions include lamellipodia, pseudopodia, filopodia, microvilli, invadopodia, and podosomes. These protrusions are often grouped as static or dynamic. Microvilli are stable, finger-like projections with a generally stable actin architecture. They are brush-like extensions on the...

mechanism of lamellipodia formation

How Cells Push Forward with Lamellipodia

Cells move forward by building lamellipodia, which are thin membrane protrusions at the leading edge. These structures are supported by a mesh of actin filaments that may be linked, branched, or unbranched. Actin works with myosin motor proteins to form the actomyosin complex in the cytoskeleton, and this complex can generate contractile stress. That contractility helps cells sense the stiffness of the extracellular matrix, or ECM, and apply force during migration. Lamellipodia begin to form...

mechanism of filopodia formation

Filopodia in Cell Movement and Contact

Filopodia are thin, actin-rich cell protrusions that help cells move and make contact. They appear in different cell types in different places and lengths. That variation suggests they can support several cell functions. In many cases, filopodia guide migrating cells during normal tissue morphogenesis and cancer metastasis. They help cells recognize the extracellular matrix and make their first contact with it. Filopodia can also act as stationary anchors or help two cells communicate. A...

cancer cell migration through invadopodia

cancer-cell-migration-through-invadopodia

How Invadopodia Help Cancer Cells Spread

Invadopodia are cell surface structures that help cancer cells break down the extracellular matrix, or ECM. The ECM is the material outside cells that gives tissues support. Invadopodia are part of a larger group called invadosomes, which also includes structures found in normal cells such as macrophages, endothelial cells, and neurons. Macrophage podosomes and tumor cell invadopodia are both invadosomes, but they are not the same. Podosomes are short-lived and last only a few minutes.

cell motility through blebbing

Blebbing in Cell Movement and Cell Death

Blebbing is a membrane change seen in cell movement and cell death. A bleb is a membrane protrusion that forms when pressure from the cytoplasm pushes the plasma membrane outward. Blebs can appear in fibroblasts, immune cells, and single-celled organisms such as amoebas. Blebs help cells move through tight spaces in the extracellular matrix, or ECM. In multicellular organisms, migrating cells must squeeze between other cells and through this three-dimensional matrix. Actin-driven protrusions...

role of myosin in cell migration

Myosin Drives Cell Adhesion and Polarity

Myosin is a motor protein that helps cells migrate by building force, strengthening attachments, and setting cell polarity. In animal cells, myosin II is the most common type. It binds and cross-links actin filaments, the protein fibers that help a cell move and change shape. Myosin II is a hexamer, or six-part complex. It has two heavy chains with globular heads and coiled-coil tails, plus two regulatory light chains and two essential light chains. The ATPase sites on the myosin heads break...

cell polarization by rho proteins

Rho Proteins in Cell Front and Rear

Cell polarity gives a cell two different sides. This uneven layout is important for embryogenesis, axon migration, glucose transport across epithelial cells, and directional cell migration. In migrating cells, signals from inside or outside the cell trigger pathways that reorganize the actin cytoskeleton and build this polarity. The Rho family proteins Cdc42, Rac, and Rho help control that process. These proteins are small GTPases, which means they act like molecular switches and can shift...

chemotaxis and direction of cell migration

chemotaxis-and-direction-of-cell-migration

How Cells Follow Chemical Gradients

Cells follow chemical gradients by sensing cues in their environment and changing their cytoskeleton to move toward or away from them. This directional movement is called chemotaxis. It helps guide many processes, including embryogenesis, development, immune response, tissue repair and regeneration, and reproduction. Chemical signals can act as attractants or repellents. In axon development, for example, chemoattractants and chemorepellents help direct a growing axon toward the correct target.

cytoskeletal coordination in cell migration

cytoskeletal-coordination-in-cell-migration

Cell Polarity During Migration

Cell polarity during migration depends on the cytoskeleton. As a cell moves, it changes shape through repeated attachment to and detachment from the substratum, the surface it grows or moves on. The cell also shifts its organelles to match these changes. This movement is controlled by a dynamic cytoskeletal network. The network includes actin filaments, intermediate filaments, and microtubules. These parts do not work alone. They communicate through cytoskeletal crosstalk, which means direct...

key terms and concepts

Explore how actin filaments power cell movement, shape membrane protrusions, and why ACTA1 and WAS gene mutations can cause disease.

Actin Filaments in Cell Movement | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

Actin Filaments in Cell Movement

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