Cell surface area regulation and membrane tension

The beautifully orchestrated regulation of cell shape and volume are centra l themes in cell biology and physiology, Though it is less well recognized, cell surface area regulation also constitutes a distinct task for cells. M aintaining an appropriate surface area is no automatic side effect of volum e regulation or shape change. The issue of surface area regulation (SAR) wo uld be moot if all cells resembled mammalian erythrocytes in being constrai ned to change shape and volume using existing surface membrane. But these e nucleate cells are anomalies, possessing no endomembrane. Most cells use en domembrane to continually rework their plasma membrane, even while maintain ing a given size or shape. This membrane traffic is intensively studied. ge nerally with the emphasis on targeting and turnover of proteins and deliver y of vesicle contents. But surface area (SA) homeostasis, including the con trolled increase or decrease of SA, is another of the outcomes of trafficki ng. Our principal aims, then, ale to highlight SAR as a discrete cellular task and to survey evidence for the idea that membrane tension is central to the task. Cells cannot directly "measure" their volume or SA, yet must regulat e both. We posit that a homeostatic relationship exists between plasma memb rane tension and plasma membrane area, which implies that cells detect and respond to deviations around a membrane tension set point. Maintenance of m embrane strength during membrane turnover, a seldom-addressed aspect of SA dynamics, we examine in the context of SAR. SAR occurs in both animal and plant cells. The review shows the latter to b e a continuing source of groundbreaking work on tension-sensitive SAR, but is principally slanted to animal cells.