Human TRPC4 blocking peptide

Neuronal dendrites have been shown to actively contribute to synaptic information transfer through the Ca2+-dependent release of neurotransmitter, although the underlying mechanisms remain elusive. This study shows that the increase in dendritic gamma-aminobutyric acid (GABA) release from thalamic interneurons mediated by the activation of 5-hydroxytryptamine type 2 receptors requires Ca2+ entry that does not involve Ca2+ release nor voltage-gated Ca2+ channels in the plasma membrane but that is critically dependent on the transient receptor potential (TRIP) protein TRPC4. These data ascribe a functional role of agonist-activated TRIP channels to the release of transmitters from dendrites, thereby indicating a principle underlying synaptic interactions in the brain.

The mammalian homologues of the Drosophila transient receptor potential (TRP) channel are plasma membrane proteins involved in the regulation of cellular Ca2+ influx. These ion channels can be activated subsequent to either depletion of Ca2+ from internal stores or through receptor-mediated processes. The mRNA expression patterns of several individual mammalian short transient receptor potential channels (TRPCs) have been described. Cross-comparisons between these data, however, are at best difficult predominantly due to the non-quantitative methods used. Furthermore there is limited data on the expression of TRPC family members in human tissues. In the present study we used a single technique, namely TaqMan real-time quantitative RT-PCR, to investigate the mRNA distribution of human TRPC1, TRPC3, TRPC4, TRPC5, TRPC6 and TRPC7 (hTRPCs) in discrete human brain areas, peripheral tissues as well as a panel of cell-lines. All hTRPCs studied were widely expressed within CNS and significant peripheral expression was often observed. Despite this, each channel exhibited a distinctive hallmark distribution profile. hTRPC1 was widely expressed in CNS and peripheral tissues, whereas hTRPC3 and hTRPC5 were predominantly expressed in tissues of CNS. hTRPC4 mRNA was detected in CNS and certain peripheral tissues such as bone, heart and prostate. hTRPC6 was homogeneously expressed throughout the CNS and peripheral tissues with the highest levels in placenta and lung. hTRPC7 mRNA was also broadly expressed in CNS as well as some peripheral tissues. The pattern of expression of the TRPCs was quite different in the various cell lines examined. TRPC3 and TRPC6 were selectively present in HEK-293 cells whilst TRPC1 was broadly distributed in the cell lines analyzed. In contrast TRPC4 and TRPC5 mRNAs were predominantly expressed in HK-2 and HEK-293 cell lines respectively. TRPC7 was selectively expressed in COS-1, COS-7 and HK-2 cell lines. These results show tissue- and cell-specific co-expression of multiple TRPC forms indicating widespread potential for formation of heteromeric channels. These data will be useful in the complex task of relating channel subunit composition to function in native cells. (C) 2002 Elsevier Science B.V. All rights reserved.