Rapid vesicular translocation and insertion of TRP channels.

The broadly expressed transient receptor potential (TRP) family of ion channels are permeant to cations, most resulting in increased intracellular calcium. However, their regulation and gating is not well understood. Here, we report that growth factor stimulation initiates the rapid translocation of the transient receptor potential ion channel, TRPC5, from vesicles held in reserve just under the plasma membrane. This process, which we term 'rapid vesicular insertion of TRP' (RiVIT), dramatically increases membrane-associated TRPC5 channels and functional TRPC5 current, resulting in tight spatial-temporal control of these Ca(2+)-permeant nonselective channels. Epidermal growth factor (EGF)-induced incorporation of functional TRP channels requires phosphatidylinositide 3-kinase (PI(3)K), the Rho GTPase Rac1 and phosphatidylinositol 4-phosphate 5-kinase (PIP(5)K alpha). The increase in TRPC5 availability affects neurite extension rates in cultured hippocampal neurons, and may be a general mechanism for initiating Ca(2+) influx and cell morphological changes in response to stimuli.

Co-stimulation of mGluR5 and N-methyl-D-aspartate receptors is required for potentiation of excitatory synaptic transmission in hippocampal neurons.

In the central nervous system, excitatory synaptic transmission is mediated by the neurotransmitter glutamate and its receptors. Interestingly, stimulation of group I metabotropic glutamate receptors (mGluRs) can either enhance or depress synaptic transmission at CA1 hippocampal synapses. Here we report that co-activation of mGluR5, a member of the group I mGluR family, and N-methyl-d-aspartate receptors (NMDARs) potentiates NMDAR currents and induces a long lasting enhancement of excitatory synaptic transmission in primary cultured hippocampal neurons. Unexpectedly, activation of mGluR5 alone fails to enhance evoked NMDAR currents and synaptic alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor (AMPAR) AMPAR currents. The observed potentiation requires an mGluR5-induced, inositol 1,4,5-trisphosphate receptor-mediated mobilization of intracellular Ca2+, which acts in concert with a protein kinase C, calcium-activated tyrosine kinase cascade to induce a long lasting enhancement of NMDAR and AMPAR currents.

A D2 class dopamine receptor transactivates a receptor tyrosine kinase to inhibit NMDA receptor transmission.

Receptor tyrosine kinases (RTKs) are membrane spanning proteins with intrinsic kinase activity. Although these receptors are known to be involved in proliferation and differentiation of cells, their roles in regulating central synaptic transmission are largely unknown. In CA1 pyramidal neurons, activation of D2 class dopamine receptors depressed excitatory transmission mediated by the NMDA subtype of glutamate receptor. This depression resulted from the quinpirole-induced release of intracellular Ca(2+) and enhanced Ca(2+)-dependent inactivation of NMDA receptors. The dopamine receptor-mediated depression was dependent on the "transactivation" of PDGFRbeta. Therefore, RTK transactivation provides a novel mechanism of communication between dopaminergic and glutamatergic systems and might help to explain how reciprocal changes in these systems could be linked to the deficits in cognition, memory, and attention observed in schizophrenia and attention deficit hyperactivity disorder.

TRPV3 is a calcium-permeable temperature-sensitive cation channel.

Transient receptor potential (TRP) proteins are cation-selective channels that function in processes as diverse as sensation and vasoregulation. Mammalian TRP channels that are gated by heat and capsaicin (>43 degrees C; TRPV1 (ref. 1)), noxious heat (>52 degrees C; TRPV2 (ref. 2)), and cooling (< 22 degrees C; TRPM8 (refs 3, 4)) have been cloned; however, little is known about the molecular determinants of temperature sensing in the range between approximately 22 degrees C and 40 degrees C. Here we have identified a member of the vanilloid channel family, human TRPV3 (hTRPV3) that is expressed in skin, tongue, dorsal root ganglion, trigeminal ganglion, spinal cord and brain. Increasing temperature from 22 degrees C to 40 degrees C in mammalian cells transfected with hTRPV3 elevated intracellular calcium by activating a nonselective cationic conductance. As in published recordings from sensory neurons, the current was steeply dependent on temperature, sensitized with repeated heating, and displayed a marked hysteresis on heating and cooling. On the basis of these properties, we propose that hTRPV3 is thermosensitive in the physiological range of temperatures between TRPM8 and TRPV1.