Intramolecular crosstalk between catalytic activities of receptor kinases

摘要

Signal modulation is important for the growth and development of plants and this process is mediated bya number of factors including physiological growth regulators and their associated signal transductionpathways. Protein kinases play a central role in signaling, including those involving pathogen responsemechanisms. We previously demonstrated an active guanylate cyclase (GC) catalytic center in thebrassinosteroid insensitive receptor (AtBRI1) within an active intracellular kinase domain resulting in dualenzymatic activity. Here we propose a novel type of receptor architecture that is characterized by afunctional GC catalytic center nested in the cytosolic kinase domain enabling intramolecular crosstalk. Thismay be through a cGMP-AtBRI1 complex forming that may induce a negative feedback mechanismleading to desensitisation of the receptor, regulated through the cGMP production pathway. We furtherargue that the comparatively low but highly localized cGMP generated by the GC in response to a ligandis sufficient to modulate the kinase activity. This type of receptor therefore provides a molecular switchthat directly and/or indirectly affects ligand dependent phosphorylation of downstream signalingcascades and suggests that subsequent signal transduction and modulation works in conjunction with thekinase in downstream signaling.