*3.2. Regulation of IDPs Abundance*

Intrinsically disordered proteins levels are carefully monitored in the cell, and changes in their abundance are associated with disease, mainly due to defective signal transduction (linked to the occurrence of some cancers [11,203]) and non-specific interactions that generate fibrillar aggregates (present in many neurodegenerative disorders [199,204]). Tight regulation can be achieved in different levels, controlling the half-lives of mRNAs encoding IDPs and the abundance of IDPs themselves. Obviously, there are outliers for these global trends and certain IDPs are present in cells in large amounts or for long periods of time [205]—usually not the IDPs involved in dynamic processes such as cell signaling. Examples include the fibrous muscle protein titin [206,207] and the curious case of tardigrade-specific IDPs, that are constitutively expressed and upregulated in some tardigrade species and are essential for desiccation tolerance [208].
