High impact information on Frq2

• Neuromuscular junctions of transgenic flies, which overexpress frequenin upon heat shock, exhibit an extraordinarily enhanced, frequency-dependent facilitation of neurotransmitter release, with properties identical to those observed in V7 junctions [1].
• Anti-frequenin antibodies stain the central and peripheral nervous system in Drosophila embryos and in larval and adult tissue sections [1].
• NCS-1/frequenin has been shown to enhance synaptic transmission in PC12 cells and Drosophila and Xenopus, respectively [2].
• Incubation with either a mammalian guanylyl cyclase-activating protein or Drosophila frequenin resulted in only mild stimulation of activity, whereas incubation of COS-7 cells expressing MsGC-II with a variety of Manduca tissue extracts failed to stimulate enzyme activity above basal levels [3].
• Using an antibody raised against Drosophila frequenin (frq), a calcium-binding protein that enhances transmitter release in Drosophila synaptic terminals, we found that frq-like immunoreactivity is prominent in many of the phasic, but not tonic nerve endings of crayfish motor neurons [4].

Biological context of Frq2

• Similar defects are observed in transgenic flies which have additional copies of the frequenin gene indicating that the phenotype can be adscribed to the overexpression of the protein [5].
• Frequenin is a Drosophila Ca2+ binding protein whose overexpression causes a chronic facilitation of transmitter release at the larval neuromuscular junction and multiple firing of action potentials [5].
• In addition, we show here that frequenin overexpression leads also to a down regulation of Shaker proteins expression [5].
• One possible explanation for the loss of IA modulation in the V7 mutation is that the excess of frequenin alters intracellular cGMP-dependent metabolic pathways responsible for the internal calcium homeostasis [6].
• These results suggest that frequenin expression is high in the frog peripheral nervous system, and may reflect a function for frequenin in synaptic transmission in vertebrates [7].

Anatomical context of Frq2

• We report here that mutants which overexpress frequenin have motor nerve terminals with reduced number and length of branches as well as number of synaptic boutons [5].
• The widespread occurrence of frq-like molecules and their differential localization in crayfish motor neurons indicate a significant role in physiology or development of these neurons [4].
• Affinity purified antibodies to frequenin recognize molecules in the neuromuscular junction, axons in the peripheral nerve, and neuronal processes in muscle spindles [7].
• Western blots of endplate regions, peripheral nerve, and brain, resulted in the labelling of a single 24 kDa band, which is the expected size for frequenin [7].
• Neuronal Ca2+ sensor 1, the mammalian homologue of frequenin, is expressed in chromaffin and PC12 cells and regulates neurosecretion from dense-core granules [8].

References