Name: how cells follow chemical gradients
Uploaded: 2023-04-30T10:17:38.000Z
Duration: 1 min 21 s
Channel: JoVE

Chemotaxis is the movement of cells in response to a chemical stimulus.
While chemoattractants direct cell movement along their concentration gradient, chemorepellents signal the cell to move away from the stimulus.
These chemical cues are usually small molecules such as peptides, sugars, and lipids, which can bind specific cell-surface receptors.
For example, the tripeptides&#160; released by bacteria, such as E.coli can bind and activate the G-protein coupled receptors or GPCRs on the surface of neutrophils.
The activated GPCRs polarize the cell by locally amplifying the signal via different signaling cascades &#8212; the Rac pathway at the cell front, and the Rho pathway at the cell rear.
This leads to cytoskeletal reorganization within the neutrophil that orients and directs its movement towards the pathogen.
In addition to diffusible chemicals, substrate-bound molecules, such as laminin glycoproteins, also induce chemotaxis.
These stimulants promote the adhesion of membrane protrusions to the substrate, thus directing cell migration along the chemical gradient.

chemotaxis and direction of cell migration

Chemotaxis and Direction of Cell Migration

Cells can detect chemical cues in their environment and reorganize the cytoskeleton to migrate toward them or away from them. This directional migration, called chemotaxis, is essential during embryogenesis and development, immune response, tissue repair and regeneration, and reproduction. These chemical cues can either attract or repel the cell&#39;s movement. For example, axon development is determined by a combination of chemoattractants and chemorepellents that direct the growing axon towards the appropriate targets.
Sensing the Gradient
Cells exhibit chemotaxis across a chemical gradient by sensing the spatial difference in the chemical concentration between the two ends of the cell. Most eukaryotic cells can detect a difference of as little as 1 to 2 percent between the cell front and rear. Smaller cells, such as prokaryotes, cannot detect this spatial gradient because the distance between the front and rear of the cell is too small. Instead, they detect the gradient temporally by moving in random bouts and identifying the direction in which the chemical concentration increases. They then continue moving along that direction for a short distance before reverting to tumbling in random directions.
Chemotaxis in Cancer
Diseases involving abnormal cell migration usually exhibit abnormal functioning of cell surface receptors or unregulated expression of ligands for these receptors. During tumor metastasis, the presence of a specific receptor and its ligands determine the likely target organ for establishing secondary tumors. For example, the common secondary tumor sites in breast cancer patients are the lungs and bone marrow. The CXCR4 receptor found in breast cancer cells binds to the ligand SDF-1&#945;, which is expressed in lung and bone marrow tissue. This ligand triggers directional migration of the metastatic cells towards these organs, thus establishing secondary tumors.

Cells can detect chemical cues in their environment and reorganize the cytoskeleton to migrate toward them or away from them. This directional migration, ...

chemotaxis-and-direction-of-cell-migration

Education

JoVE Core

Cell Biology

Unit 1

Cell Polarization and Migration

KEY TERMS AND CONCEPTS

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. These signals give cells information about where to move next.

Cells detect a gradient in different ways. Most eukaryotic cells sense a spatial difference in chemical concentration between the front and rear of the cell. They can detect a change as small as 1 to 2 percent. Smaller cells, such as prokaryotes, are too small to sense that kind of front-to-back difference.

Prokaryotes use a temporal method instead. They move in random bouts and check whether the chemical concentration is increasing. If it is, they keep moving in that direction for a short distance. Then they return to random tumbling and try again.

Chemotaxis also plays a role in cancer when cell migration goes wrong. Abnormal movement is often linked to faulty cell surface receptors or to unregulated expression of ligands, which are molecules that bind to receptors. During tumor metastasis, the receptor and its ligands can help determine where secondary tumors form. In breast cancer, secondary tumors often appear in the lungs and bone marrow because the CXCR4 receptor on breast cancer cells binds to SDF-1α, which is expressed in those tissues. That binding directs metastatic cells toward those organs.

How Cells Follow Chemical Gradients

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 polymerization and cell motility

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...

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...

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

Learn how cells sense chemical gradients, use chemoattractants and chemorepellents, and direct migration during development, immunity, and cancer spread.

How Cells Follow Chemical Gradients | 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.

How Cells Follow Chemical Gradients

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