High impact information on Syx1A

• Complete absence of syx-1A causes subtle morphological defects in the peripheral and central nervous systems, affects nonneural secretory events, and entirely abolishes neurotransmitter release [1].
• The most extensively studied candidate for the Ca(2+)-sensing trigger is synaptotagmin I, whose Ca(2+)-dependent interactions with acidic phospholipids and syntaxin have largely been ascribed to its C(2)A domain, although the C(2)B domain also binds Ca(2+) (refs 7, 8) [2].
• Therefore, UNC-13 binding to the N terminus of syntaxin may promote the open configuration of syntaxin [3].
• Thus, it is likely that UNC-13 primes synaptic vesicles for fusion by promoting the open configuration of syntaxin [3].
• Elimination of dunc-13 expression abolished synaptic transmission, an effect comparable only to removal of the core complex proteins Syntaxin and Synaptobrevin [4].

Biological context of Syx1A

• We used a targeted mutagenesis approach to eliminate specific syntaxin binding interactions and demonstrate that Drosophila syntaxin 1A plays multiple regulatory roles in neurotransmission in vivo [5].
• The PKC-catalyzed phosphorylation of Munc-18 inhibits its interaction with syntaxin [6].
• The relation of protein binding to function: what is the significance of munc18 and synaptotagmin binding to syntaxin 1, and where are the corresponding binding sites [7]?
• In synaptic transmission, vesicles are proposed to dock at presynaptic active zones by the association of synaptobrevin (v-SNARE) with syntaxin (t-SNARE) [8].
• The deduced amino acid sequence of the Dsynt1 cDNA cloned is highly homologous to rat syntaxin 1A [9].

Anatomical context of Syx1A

• Biochemical studies suggest that syntaxin 1A participates in multiple protein-protein interactions in the synaptic terminal, but the in vivo significance of these interactions is poorly understood [5].
• These results suggest that the PKC-catalyzed phosphorylation of Munc-18 plays an important role in regulating the interaction of Munc-18 with syntaxin and thereby the docking and/or the fusion of synaptic vesicles with the presynaptic plasma membrane [6].
• The Q-SNARE syntaxin 1 is a central component of the synaptic membrane fusion machinery [7].
• The syntaxin Avalanche (Avl) localizes to early endosomes, and loss of avl results in the cellular accumulation of specific membrane proteins, including the Notch signalling receptor and the polarity determinant Crumbs (Crb) [10].
• Hypomorphic mutations in syntaxin-1A or n-synaptobrevin, which also disrupt neurotransmitter release, did not affect synapse proliferation at the neuromuscular junction, suggesting calcium entry through presynaptic N-type calcium channels, not neurotransmitter release per se, is important for synaptic growth [11].

Associations of Syx1A with chemical compounds

• Overexpression of cysteine-string proteins in Drosophila reveals interactions with syntaxin [12].
• In contrast, a separate Ca2+-dependent interaction between synaptotagmin and syntaxin, a component of the fusion apparatus, occurs with an EC50 value of approximately 100 microM Ca2+ and involves the synergistic action of both C2 domains of synaptotagmin [13].

Physical interactions of Syx1A

• In vitro studies, however, show that SNAP-24 can form core complexes with syntaxin and both synaptic and non-synaptic v-SNAREs [14].
• Taken together, these results suggest that ROP interacts with syntaxin in vivo and is a rate-limiting regulator of exocytosis that performs both positive and inhibitory functions in neurotransmission [15].

Regulatory relationships of Syx1A

• These vesicles are mature and functional since spontaneous vesicle fusion persists in the absence of n-synaptobrevin and since vesicle fusion is triggered by hyperosmotic saline in the absence of syntaxin [8].

Other interactions of Syx1A

• Additionally, we identify and characterize a syntaxin Ca2+ effector domain, which may spatially organize the Ca2+ channel, cysteine string protein, and synaptotagmin for effective excitation-secretion coupling in the presynaptic terminal [5].
• Both viable and lethal alleles of coro show genetic interactions with syntaxin1A, a gene required for membrane trafficking [16].
• This resulted in a notched-wing phenotype, the severity of which was enhanced when combined with mutants of VAMP/Synaptobrevin or Syntaxin, indicating that it results from impaired membrane trafficking [17].
• The UNC-13 protein family has been suggested to be critical for synaptic vesicle dynamics based on its interactions with Syntaxin, Munc-18 and Doc 2alpha [4].
• The neuron-specific proteins SNAP-25 (synaptosome-associated protein 25 kDa), synaptobrevin and syntaxin, are localized to presynaptic terminals in mammals and have been found to associate with proteins involved in vesicle docking and membrane fusion [18].

Analytical, diagnostic and therapeutic context of Syx1A

• We demonstrate that two-dimensional gel electrophoresis in conjunction with mass spectrometry is a suitable tool for the identification of intrinsic membrane proteins, and we show that among them a syntaxin, AtSyp122, is phosphorylated rapidly in response to flg22 [19].

References