User:Dimphled/sandbox

Apoptotic Function
Blebbing is one of the defined features of apoptosis, separating its distinction from necrotic cells. During apoptosis (programmed cell death), the cell's cytoskeleton breaks up and causes the membrane to bulge outward. These bulges may separate from the cell, taking a portion of cytoplasm with them, to become known as apoptotic blebs. Successful blebbing physically separates the bulge from the parent plasma membrane, rendering the apoptotic cell without the structural integrity required to maintain essential transmembrane gradients and rigidity. Phagocytic cells eventually consume these fragments and the components are recycled.

Two types of blebs are recognized in apoptosis. Initially, small surface blebs are formed. During later stages, larger so-called dynamic blebs may appear, which may carry larger organelle fragments such as larger parts of the fragmented apoptotic cell nucleus. In contrast to nonapoptotic blebbing which may be reversible, apoptotic types are irreversible.

Cell Migration Function
Along with lamellipodia, blebs serve an important role in cell migration. Movement and general motility of cells is critical in processes such as immune response cell locomotion. Migrating cells are able to polarize the formation of blebs so blebbing only occurs on the leading edge of the cell. A 2D moving cell is able to use adhesive molecules to gain traction in its environment while blebs form at the leading edge. This allows the bleb to find its way to the site in inflammation or infection. Streamlined diffusion of the cytoplasm will propel the cell towards that direction, making it appear as if the bleb is swimming due to its nonuniform shape.

By forming a bleb, the center of mass of the cell shifts forward and an overall movement of cytoplasm is accomplished. When cortex-relaxing drugs lower the pressure of a blebbing cell on a designated side, the motion stops, representing the non-equilibrated nature of intracellular hydrostatic pressure made possible by the cellular cytosolic network capable of fluid motion. Cells have also been known to accomplish 3D bleb-based movement through a process called chimneying. In this process, cells exert hydrostatic pressure on the top and bottom substrates by squeezing themselves, causing a bleb on the leading edge to grow and the cell to have a net movement forward. The locomotion and polarity of cells are a crucial component involved in cancer metastasis, as the induction of artificial movement rearrange bleb formations to aid treatment.