Beta 1 Integrins

A mammal’s cell migrates by having their actin filaments polymerize, or build up, that causes a part of the cell membrane to extend out. This part is called the leading edge. The leading edge attaches to the extracellular membrane (ECM) in order to pull itself forward in order to travel. Actin binding proteins regulate position, speed, and persistence of the leading edges.

The objective of this research was to figure out if leading edges of migratory cells work together with adhesion receptors to cause cell migration though the ECM.

The scientists hypothesized that the leading edges of migratory cells search for places in the ECM to adhere to.

The scientists observed the small ripples on the cell membranes under a high-contrast differential interference contrast, which is a type of microscope that is good to use for observing cells.

The scientists tested to see if an increase actin polymerization causes the cells to migrate through the ECM by comparing them with the location of integrins.

Using a fluoresced antibody, the scientists observed the clustering of beta 1 integrins that occurred at the same time as actin polymerization at the ripples of the cell membrane.

The scientists tested the relationship between actin polymerization and activated beta 1 integrins by changing the way that the actin worked. They decreased the number of polymerizing actin ends by capping with with cytochalasin D in order to see if that would cause the amount of activated beta 1 integrins to decrease. They also increased the actin polymerizing ends with the stabilizer, jasplakinolide in order to see if that would cause the amount of activated beta 1 integrins to

increase.
In order to see whether or not beta 1 integrins interact with polymerizing actin, the cell membranes and cell membrane proteins were removed with Trinton X-100, but have the cytoskeleton and cytoskeletally associated proteins stay.
Increases in actin polymerization occur at small ripples at the leading edges of migratory fibroblasts. These ripples move from side to side. Cytochalasin D makes there be ripples less often. The ripples move faster from side to side than filopodia do. The ripples also move faster from side to side than the backward protrusion movements caused by actin growing at one end and shrinking at the other.
The polymerization of actin ends determines the locations of the activated beta 1 integrins at the leading edges. When the actin is blocked, there is a decrease in beta 1. There is an increase in beta 1 when there are more free ends of actin. The inhibition of myosin II ATPase does not affect how many integrins and actin ends there are. Activated beta 1 integrins are also in the pointy tips of cell protrusions called growth cone filopodia, which are caused by actin polymerization.
Polymerization of actin near the cell membrane causes there to be a leading edge. The leading edge causes the cell to migrate by adhering to the ECM and then pulling itself forward. Also, cells with well-developed adhesive contacts can be influenced into making small changes in their migration directions without detaching and forming new matrix connections.