Neurokinin-1 Receptor Resensitization Precedes Receptor Recycling

Abstract

Following agonist binding, neurokinin-1 receptors undergo rapid desensitization followed by internalization and recycling. Desensitization requires receptor phosphorylation but does not require internalization, whereas resensitization is thought to require internalization and recycling. Our previous data, however, have suggested that, following activation and desensitization, the return of responsiveness to the neurokinin-1 agonist substance P (termed "resensitization") occurs hours before internalized receptors are recycled back to the plasma membrane. To further investigate this novel mechanism of neurokinin-1 receptor resensitization, we have studied the time courses of neurokinin-1 receptor responsiveness, recycling, and dephosphorylation by measuring cellular Ca 2ϩ responses, ligand-receptor binding, and receptor phosphorylation, respectively. Concentration-response curves and competition binding curves were obtained at various times following desensitization. The effects of the nonhydrolyzable GTP analog Gpp(NH)p on substance P binding were also studied to assess receptor-G protein coupling. After receptor activation and desensitization, Ca 2ϩ signaling in response to substance P occurred within 90 min, whereas the return of receptor binding required 240 min. Receptor dephosphorylation was greater than 90% complete 20 min after agonist washout. In addition, the return of substance P responsiveness coincided with a return in sensitivity of substance P binding to Gpp(NH)p, indicating a return in receptor-G protein coupling. These data show that the resensitization of responsiveness to substance P precedes receptor recycling. This may result from a conversion of nonfunctional neurokinin-1 receptors to functional receptors at the plasma membrane.

Neurokinin‐1 receptor desensitization to consecutive microdialysis infusions of substance P in human skin

“…In these few subjects, the increase in CVC to the second dose may be related to differential processes of desensitization and internalization. Recently, Bennett et al (2005) have shown that NK 1 receptor resensitization occurs prior to NK 1 receptor recycling to the cell surface. In this study, Bennett et al (2005) suggest that resensitization of the receptors occurs at the level of the G proteins and that there may be two different NK 1 receptors, one type which undergoes internalization and another type which does not undergo internalization upon ligand binding.…”

“…Recently, Bennett et al (2005) have shown that NK 1 receptor resensitization occurs prior to NK 1 receptor recycling to the cell surface. In this study, Bennett et al (2005) suggest that resensitization of the receptors occurs at the level of the G proteins and that there may be two different NK 1 receptors, one type which undergoes internalization and another type which does not undergo internalization upon ligand binding. In this scenario, receptors that undergo internalization would need to be recycled back to the cell surface in order to be resensitized.…”

Tachykinins and their functions in the gastrointestinal tract

“…Furthermore, there may be an additional mechanism for restoration of responsiveness. It has been shown that the restoration of responsiveness of NK1 receptors to SP can precede receptor recycling [60]. This may result from a conversion of non-functional NK1 receptors to functional receptors at the plasma membrane.…”

Roles of proteolysis in regulation of GPCR function

“…An additional role for ECE‐1‐mediated cleavage of SP emerged following the observation that resensitization of SP‐induced intracellular calcium mobilization precedes recycling of the NK 1 receptor (Bennett et al ., 2002; 2005; Murphy et al ., ). It is known that agonist‐unoccupied GPCRs are desensitized by phosphorylation of serine and threonine residues by the second messenger kinases, PKA and PKC (Roth et al ., ; Pitcher et al ., ; Dery et al ., ).…”