Entosis

Derived from the Greek word "entos," meaning "inside," entosis refers to a unique cellular process where one cell engulfs and digests another cell. This process, sometimes referred to as "cellular cannibalism," plays a crucial role in various physiological and pathological contexts.

Mechanisms of Entosis

Entosis involves a complex set of molecular and cellular events that orchestrate the engulfment of one cell by another. Unlike traditional forms of cell death, such as apoptosis or necrosis, entosis represents a form of cell-in-cell death. The process typically begins with the recognition and binding of the engulfing cell (the "eater" or host cell) to the target cell (the "prey" or entrapped cell). Adhesion molecules and signaling pathways play essential roles in facilitating this initial interaction.

One key player in entosis is the Rho family of GTPases, which regulates actin dynamics and facilitates the deformation of the plasma membrane to allow cell engulfment. Additionally, proteins such as E-cadherin, a cell adhesion molecule, have been implicated in mediating the attachment between the host and prey cells. As the engulfment progresses, the prey cell is internalized within the host cell in a membrane-bound structure known as an "entotic vacuole."

Cellular Consequences of Entosis

The fate of the entrapped cell within the entotic vacuole can vary. In some cases, the prey cell undergoes a form of cell death known as entotic cell death, marked by the degradation of its cellular components within the vacuole. Alternatively, the entrapped cell may escape, either by a process called "cell-in-cell" expulsion or through mechanisms that allow it to survive and exit the host cell.

Physiological Functions

Entosis is not merely a cellular oddity; it serves important physiological functions in various biological processes. During embryonic development, entosis contributes to tissue remodeling by eliminating excess or mislocalized cells. Additionally, entosis plays a role in maintaining tissue homeostasis and eliminating damaged or aged cells, serving as a form of quality control within tissues.

Pathological Implications

While entosis is a crucial process in normal physiological contexts, dysregulation of this phenomenon has been linked to certain pathological conditions. Atypical entosis has been observed in cancer, where it may contribute to tumor progression by promoting cell survival, invasion, and resistance to therapy. Researchers are actively investigating the role of entosis in cancer biology and its potential as a target for therapeutic interventions.