A previously unknown mechanism involving the protein Scribble helps maintain polarity in cells, according to a Northwestern Medicine study published.
This new mechanism sheds light on the complex web of systems that keep cells pointing in the correct direction, according to Sergey Troyanovsky, PhD, professor of Dermatology, of Cell and Developmental Biology and senior author of the study.
"This is the architecture of the cell, like how individual buildings come together to form the whole city."
Cell polarity dictates an orientation for all cells, providing a matrix-like structure that makes up all tissue in the body. Apical and basal polarity define "up" and "down."
This polarity is maintained by certain proteins, which sit on the apical (top) or basal/lateral (bottom) cell membrane and signal to one another or to cell-cell junctions. However, exactly how these proteins regulate and communicate to one another was unknown.
In the current study, investigators examined the protein Scribble, a well-known protein involved in development of the lateral plasma membrane. About one-third of this protein is sufficient to maintain correct polarity of the cells, but the mechanism of this activity was unclear.
Searching for this mechanism, the scientists measured the breadth of protein interactors on the cell membrane that are present in the functional Scribble and its mutant that is unable to maintain polarity. The difference in interactors between these two proteins is just five protein interactors, according to the study. One of these protein is the well-known protein phosphatase 1 (PP1).
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