Quality control in cell biology.

Abstract

![][1] Morphology of intracellular membranes revealed by in situ cryo–electron tomography. This 3D segmentation of a cellular tomogram contains a representative Golgi stack: cis cisternae (green), cis vesicles (light green), medial cisternae (magenta), medial vesicles (light pink), the trans cisterna (blue), trans vesicles (light blue), and the trans Golgi network (purple). The endoplasmic reticulum is highlighted in yellow. Other membranes, the nuclear envelope, nuclear pore complexes, and ribosomes are shown in gray. IMAGE: Y. S. BYKOV ET AL., eLIFE 6 , e32493 (2017) Our cells are in a constant state of flux—growing, dividing, and continually responding to their environment. To maintain optimal performance of these processes, a range of quality control mechanisms is required. Quality control within cells involves a variety of self-regulating activities, one of which keeps protein synthesis in balance with the breakdown of dysfunctional proteins. Similarly, the components from which molecules are built must be recycled and redistributed to ensure that cellular systems can continue running. Other pathways are important to guarantee that RNA is created faithfully and shuttled through the cell to make the right proteins at the right time. Moreover, DNA quality control pathways maintain the genetic code while enabling cellular survival and proliferation. Our cells contain a variety of organelles that must cooperate during growth and cell regulation. A case in point is the need for mitochondria, which have their own limited genome, to coordinate their metabolism and growth with that of the cell as a whole. A sophisticated set of feedback controls is required to keep the nucleus and the mitochondria in sync. Failures in cellular quality control are linked to cancer, neurodegeneration, and other developmental diseases and diseases of aging. Deciphering the mechanistic underpinnings of these quality control processes, whether they have limits, and how they are regulated as disease develops should help us understand, prevent, and even treat a wide range of conditions. [1]: /embed/graphic-1.gif