In addition to disposal of misfolded/damaged proteins, the UPS also plays a key role in the regulation of many fundamental cellular functions, including apoptosis, cell cycle regulation, antigen processing, and transcriptional regulation via controlling the degradation of normal regulatory proteins [ 21– 23].
Intracellular redox state is a critical factor for fundamental cellular functions, including regulation of the activities of various metabolic enzymes as well as ROS production and elimination.
Heme (Fe2+ protporphyrin IX) is a ubiquitous and essential tetrapyrrole molecule that performs a wide array of fundamental physiological functions, including oxygen transport, electron transfer, and transcriptional regulation.
Microtubules are critical elements in a variety of fundamental cellular functions, including formation and maintenance of cell shape, transportation of vesicles and protein complexes, and regulation of motility and cell division[1].
The Ras superfamily of small molecular weight GTPases controls fundamental cellular functions including those essential for invasive growth.
The signal transduction pathways subverted by oncoproteins govern fundamental cell functions, including proliferation, cell cycle regulation, and apoptosis [ 5].
ERK features more than 150 substrates thereby regulating many fundamental cellular functions, including proliferation, differentiation, transformation, apoptosis and metabolism [ 39].
As one of the critical organelles, endoplasmic reticulum (ER) carries out fundamental biological functions including protein folding, protein modification, lipid synthesis and calcium signaling [ 10].
It plays crucial roles in various fundamental cell functions, including mitotic regulation, maintenance of cell morphology, intracellular motility and macromolecules and organelles trafficking [ 14, 15].
An obvious problem with this view is how to rationalise that this pathway controls many and diverse fundamental cellular functions including proliferation, differentiation, transformation and apoptosis.
