Blebbing

A cellular process involving the formation of bulges in the plasma membrane

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Blebbing is a cellular process characterized by the formation of bulges, or blebs, in the plasma membrane of a cell. This phenomenon is observed in various physiological and pathological contexts, including apoptosis, cell movement, and cell division.

Mechanism

Blebbing occurs when the cytoskeleton detaches from the plasma membrane, allowing the membrane to balloon outward. This process is driven by the contraction of the actin-myosin cortex, which generates pressure that pushes the membrane outward. The bleb initially forms as a spherical protrusion, which can either retract back into the cell or stabilize and mature into a more permanent structure.

The formation of blebs involves several key steps:

Initiation: The detachment of the cytoskeleton from the plasma membrane, often triggered by changes in intracellular calcium levels or signaling pathways. Expansion: The actin-myosin cortex contracts, generating pressure that pushes the membrane outward to form a bleb. Stabilization: The bleb can stabilize if the actin cortex reforms beneath the membrane, providing structural support. Retraction: The bleb may retract if the actin cortex reattaches to the membrane, pulling it back into the cell.

Functions

Blebbing serves various functions depending on the cellular context:

• Apoptosis: During programmed cell death, blebbing is a hallmark feature. It facilitates the disassembly of the cell into apoptotic bodies, which are then phagocytosed by neighboring cells or immune cells.
• Cell Movement: In some cells, such as amoeboid cells, blebbing is used as a mechanism for movement. The formation and retraction of blebs can propel the cell forward.
• Cell Division: Blebbing can occur during cytokinesis, the final stage of cell division, to help separate the daughter cells.

Pathological Implications

Abnormal blebbing is associated with various diseases and conditions. For example, excessive blebbing can occur in cancer cells, contributing to their invasive properties. Additionally, certain genetic disorders affecting the cytoskeleton can lead to abnormal blebbing and associated cellular dysfunctions.

Also see

• Apoptosis
• Cytoskeleton
• Cell movement
• Cytokinesis
• Plasma membrane