Biophysical assay for tethered signaling reactions reveals tether-controlled activity for the phosphatase SHP-1
Salas, Citlali Solis
Isaacson, Samuel A.
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CitationJesse Goyette, Citlali Solis Salas, Nicola Coker-Gordon, Marcus Bridge, Samuel A Isaacson, Jun Allard, Omer Dushek. 2017. "Biophysical assay for tethered signaling reactions reveals tether-controlled activity for the phosphatase SHP-1.." Sci Adv, Volume 3, Issue 3: e1601692.
Tethered enzymatic reactions are ubiquitous in signaling networks but are poorly understood. A previously unreported mathematical analysis is established for tethered signaling reactions in surface plasmon resonance (SPR). Applying the method to the phosphatase SHP-1 interacting with a phosphorylated tether corresponding to an immune receptor cytoplasmic tail provides five biophysical/biochemical constants from a single SPR experiment: two binding rates, two catalytic rates, and a reach parameter. Tether binding increases the activity of SHP-1 by 900-fold through a binding-induced allosteric activation (20-fold) and a more significant increase in local substrate concentration (45-fold). The reach parameter indicates that this local substrate concentration is exquisitely sensitive to receptor clustering. We further show that truncation of the tether leads not only to a lower reach but also to lower binding and catalysis. This work establishes a new framework for studying tethered signaling processes and highlights the tether as a control parameter in clustered receptor signaling.