Optical chemosensors for the detection of proximally phosphorylated peptides and proteins

Abstract

Proximal multi-site phosphorylation is a critical post-translational modification in protein biology. The additive effects of multiple phosphosite clusters in close spatial proximity triggers integrative and cooperative effects on protein conformation and activity. Proximal phosphorylation has been shown to modulate signal transduction pathways and gene expression, and as a result, is implicated in a broad range of disease states through altered protein function and/or localization including enzyme overactivation or protein aggregation. The role of proximal multi-phosphorylation events is becoming increasingly recognized as mechanistically important, although breakthroughs are limited due to a lack of detection technologies. To date, there is a limited selection of facile and robust sensing tools for proximal phosphorylation. Nonetheless, there have been considerable efforts in developing optical chemosensors for the detection of proximal phosphorylation motifs on peptides and proteins in recent years. This review provides a comprehensive overview of optical chemosensors for proximal phosphorylation, with the majority of work being reported in the past two decades. Optical sensors, in the form of fluorescent and luminescent chemosensors, hybrid biosensors, and inorganic nanoparticles, are described. Emphasis is placed on the rationale behind sensor scaffolds, relevant protein motifs, and applications in protein biology.

Fig. 1. (A) Chemical structure of phosphorylated amino acids phosphoserine (pS), phosphothreonine (pT) and phosphotyrosine (pY); (B) Illustration of a representative phosphorylation/dephosphorylation signal transduction pathway.

Fig. 2. Illustration of the types of optical sensors for proximal phosphorylation detection.

Fig. 3. Chemical structure of fluorescent chemosensors 1–9.

Fig. 4. Chemical structure of lanthanide chemosensors 10–12.

Fig. 5. Structures of hybrid biosensors 13 and 14.

Fig. 6. Structures of inorganic nanoparticle sensors 15 and 16.

Fig. 7. Main binding mechanisms of sensors for proximal phosphorylation. (A) Two or more Zn(ii)-chelate receptors within one sensing scaffold binding to a proximal phosphorylation motif; (B) two individual Zn(ii)-chelate receptor molecules detecting proximal phosphosites with excimer reporting; (C) lanthanide binding to phosphosites with antenna sensitization.