241 human active and 13 inactive phosphatases in total;
194 phosphatases have substrate data;
336 protein substrates;
83 non-protein substrates;
1215 dephosphorylation interactions;
299 KEGG pathways;
876 Reactome pathways;
last scientific update: 11 Mar, 2019
last maintenance update: 01 Sep, 2023
Required for vesicle-mediated transport Catalyzes thefusion of transport vesicles within the Golgi cisternae Is alsorequired for transport from the endoplasmic reticulum to the Golgistack Seems to function as a fusion protein required for thedelivery of cargo proteins to all compartments of the Golgi stackindependent of vesicle origin Interaction with AMPAR subunitGRIA2 leads to influence GRIA2 membrane cycling (By similarity)
Communication between neurons is mediated by the release of neurotransmitter from synaptic vesicles (SVs). At the nerve terminal, SVs cycle through repetitive episodes of exocytosis and endocytosis. SVs are filled with neurotransmitters by active transport. The loaded SVs are then docked at a specialized region of the presynaptic plasma membrane known as the active zone, where they undergo a priming reaction. Upon arrival of an action potential, Ca2+ enters through voltage-gated channels and neurotransmitter is released by exocytosis, usually in less than a millisecond. After fusion, the vesicle is retrieved by endocytosis and reloaded for another round of exocytosis.
Gamma aminobutyric acid (GABA) is the most abundant inhibitory neurotransmitter in the mammalian central nervous system (CNS). When released in the synaptic cleft, GABA binds to three major classes of receptors: GABAA, GABAB, and GABAC receptors. GABAA and GABAC receptors are ionotropic and mediate fast GABA responses by triggering chloride channel openings, while GABAB receptors are metabotropic and mediate slower GABA responses by activating G-proteins and influencing second messenger systems. GABAA receptors, the major sites for fast inhibitory neurotransmission in the CNS, are regulated by phosphorylation mechanisms, affecting both their functional properties and their cell surface mobility and trafficking. GABA release by the presynaptic terminal is negatively regulated by GABAB autoreceptors, and is cleared from the extracellular space by GABA transporters (GATs) located either on the presynaptic terminal or neighboring glial cells.
In the kidney, the antidiuretic hormone vasopressin (AVP) is a critical regulator of water homeostasis by controlling the water movement from lumen to the interstitium for water reabsorption and adjusting the urinary water excretion. In normal physiology, AVP is secreted into the circulation by the posterior pituitary gland, in response to an increase in serum osmolality or a decrease in effective circulating volume. When reaching the kidney, AVP binds to V2 receptors on the basolateral surface of the collecting duct epithelium, triggering a G-protein-linked signaling cascade, which leads to water channel aquaporin-2 (AQP2) vesicle insertion into the apical plasma membrane. This results in higher water permeability in the collecting duct and, driven by an osmotic gradient, pro-urinary water then passes the membrane through AQP2 and leaves the cell on the basolateral side via AQP3 and AQP4 water channels, which are constitutively expressed on the basolateral side of these cells. When isotonicity is restored, reduced blood AVP levels results in AQP2 internalization, leaving the apical membrane watertight again.
COPII components (known as Sec13p, Sec23p, Sec24p, Sec31p, and Sar1p in yeast) traffic cargo from the endoplasmic reticulum to the ER-Golgi intermediate compartment (ERGIC). COPII-coated vesicles were originally discovered in the yeast Saccharomyces cerevisiae using genetic approaches coupled with a cell-free assay. The mammalian counterpart of this pathway is represented here. Newly synthesized proteins destined for secretion are sorted into COPII-coated vesicles at specialized regions of the ER. These vesicles leave the ER, become uncoated and subsequently fuse with the ERGIC membrane
Trafficking of GluR2-containing receptors is governed by protein protein interactions that are regulated by phosphorylation events. GluR2 binds NSF and AP2 in the proximal C terminal region and binds PICK and GRIP1/2 in the extreme C terminal region. GluR2 interaction with NSF is necessary to maintain the synaptic levels of GluR2-containing AMPA receptors both at basal levels and under conditions of synaptic activity. GluR2 interaction with GRIP helps anchor AMPA receptors at the synapse. Phosphorylation of GluR2 at S880 disrupts GRIP interaction but allows binding of PICK. PICK is activated by Ca sensitive Protein kinase C (PKC). Under basal conditions, in hippocampal synapse, GluR2-containing AMPA receptors (GluR2/GluR3) constitutively recycle between the synapse and the endosome by endocytosis and exocytosis. GRIP anchors the receptors at the synapse while PICK interaction internalizes the receptors and NSF helps maintain the synaptic receptors. Cerebellar stellate cells mainly contain GluR3 homomers as Ca permeable receptors. The interaction of GluR3 and GRIP is disrupted by PICK interaction by phosphorylation of equivalent of S880 residue in GluR3. Under conditions of repetitive presynaptic activity, there is PICK dependent removal of GluR2-lacking AMPA receptors and selective incorporation of GluR2-containing AMPA receptors at the synapse. The GluR2-containing AMPA receptors are first delivered to the surface by PICK and mobilized to the synapse by NSF dependent mechanism (Liu SJ and Cull-Candy SG Nat Neurosci
The ERGIC (ER-to-Golgi intermediate compartment, also known as vesicular-tubular clusters, VTCs) is a stable, biochemically distinct compartment located adjacent to ER exit sites (Ben-Tekaya et al, 2005; reviewed in Szul and Sztul, 2011). The ERGIC concentrates COPII-derived cargo from the ER for further anterograde transport to the cis-Golgi and also recycles resident ER proteins back to the ER through retrograde traffic. Both of these pathways appear to make use of microtubule-directed COPI-coated vesicles (Pepperkok et al, 1993; Presley et al, 1997; Scales et al, 1997; Stephens and Pepperkok, 2002; Stephens et al, 2000; reviewed in Lord et al, 2001; Spang et al, 2013)
Retrograde traffic from the cis-Golgi to the ERGIC or the ER is mediated in part by microtubule-directed COPI-coated vesicles (Letourneur et al, 1994; Shima et al, 1999; Spang et al, 1998; reviewed in Lord et al, 2013; Spang et al, 2013). These assemble at the cis side of the Golgi in a GBF-dependent fashion and are tethered at the ER by the ER-specific SNAREs and by the conserved NRZ multisubunit tethering complex, known as DSL in yeast (reviewed in Tagaya et al, 2014; Hong and Lev, 2014). Typical cargo of these retrograde vesicles includes 'escaped' ER chaperone proteins, which are recycled back to the ER for reuse by virtue of their interaction with the Golgi localized KDEL receptors (reviewed in Capitani and Sallese, 2009; Cancino et al, 2013)
The mammalian Golgi consists of at least three biochemically distinct cisternae, cis-, medial- and trans (reviewed in Szul and Sztul, 2011; Day et al, 2013). The structure and function of the Golgi are tightly interconnected, such that proteins that are required for protein transport through the Golgi are often also required for the organization of the Golgi stacks, and vice versa (reviewed in Liu and Storrie, 2012; Liu and Storrie, 2015; Chia and Gleeson, 2014; Munro, 2011). Newly synthesized proteins from the ER and ERGIC are received at the cis face of the Golgi and flow through to the trans-Golgi before being released to the trans-Golgi network (TGN) for further secretion to the endolysosomal system, plasma membrane or extracellular region. Retrograde flow from the trans- to cis-cisternae moves endocytosed cargo from the extracellular region, the plasma membrane and the endolysosomal system back towards the ER. Intra-Golgi retrograde traffic also returns resident Golgi proteins to their appropriate cisternae, in this way facilitating cisternal remodeling or maturation (reviewed in Boncompain and Perez, 2013; Day et al, 2013). Intra-Golgi traffic in both directions is mediated by COPI carriers, with specificity of transport being determined at least in part by the complement of SNAREs, RABs and tethering proteins involved (reviewed in Szul and Sztul, 2011; Spang 2013; Willet et al, 2013; Chia and Gleeson, 2014)
The trans-Golgi network is the docking site for retrograde cargo from the endolysosomal system and the plasma membrane. Typical cargo includes recycling resident TGN proteins such as TGOLN2 (also known as TGN46), receptors such as the mannose-6-phosphate receptors and toxins like Shiga, cholera and ricin which use the retrograde trafficking machinery to 'hitchhike' back through the secretory system for release into the cytoplasm (reviewed in Johannes and Popoff, 2008; Pfeffer, 2011; Sandvig et al, 2013). These cargo are trafficked from the endocytic system in a clathrin- and AP1-dependent manner that is described in more detail in the \Trans-Golgi network budding pathway\(just not yet). In general, it appears that vesicles are uncoated prior to their tethering and fusion at the TGN. At the TGN, at least 2 distinct tethering pathways exist. A RAB6-dependent pathway contributes to the fusion and docking of vesicles from the early endocytic pathway. These vesicles, which carry cargo such as TGOLN2 and toxins, dock at the TGN through interactions with TGN-localized Golgin tethers and with the multisubunit tethering complexes COG and GARP (reviewed in Bonafacino and Rojas, 2006; Bonafacino and Hierro, 2011; Pfeffer, 2011). In contrast, mannose-6-phosphate receptors appear to traffic from late endosomes to the TGN through a RAB9- and PLIN3-dependent pathway