TRP channels Tibor Rohacs

Calcium Three major compartments: Intracellular: signaling ion, very low concentration (~ 100 nM) Extracellular: ~2.5 mM total, ~1.25 mM ionized Bones: hydroxyapatite crystals: Ca 10 (PO 4 ) 6 (OH) 2

Calcium signaling From: Clapham, D.E., et al. Nat. Rev. Neurosci. 2, (2001). GPCR-s: Angiotensin II Acetylcholine (M1 M3) Adrenergic alpha-1 Thrombin Metabotropic GluR RTK-s EGF, NGF, BDNF etc Other factors Sperm  oocyte Light (invertebrates)

Capacitative (store operated) Ca 2+ entry (Putney) From: Putney, J.W., Jr. Cell Calcium 11, (1990).

Calcium Release Activated Calcium current (I CRAC ) From: Hoth, M. & Penner, R. Nature 355, (1992).

From: Minke, B. & Cook, B. Physiol Rev. 82, (2002). Invertebrate Phototransduction

Transient Receptor Potential From: Minke, B. & Cook, B. Physiol Rev. 82, (2002).

TRP channels and capacitative calcium entry From: Zhu, X., et al. Cell 85, (1996). From: Vaca, L., et al. Am. J. Physiol. 267 C1501-C1505 (1994). +thapsigargin

I CRAC and TRP channels I CRAC TRP Ca 2+ selectiveNon selective cation channel Inwardly rectifyingOutwardly rectifying Very small single channel conductance Measurable single channel conductance Store depletion activates Store depletion activates (sometimes)

Direct activation of TRP channels by the IP 3 receptor From: Kiselyov, K., et al. Nature 396, (1998).

DAG activation of TRPC3,6,7 From: Hofmann,T., et al. Nature 397, (1999).

PIP 2 inhibition of TRPL From: Estacion, M., et al. J. Physiol 530, 1-19 (2001).

The TRPC (Classical) family Homologues of TRP and TRPL Seven members TRPC1-7 Are activated upon PLC activation –Store Operated –DAG  TRPC3,6,7 –IP 3 receptor  direct interaction –PIP 2 inhibits TRPL channels, other TRPC-s are not tested yet No general paradigm on how PLC activates these TRPC channels

Thermosensation Hot Cold Capsaicin (chili pepper) sensitizes to warm temperature Menthol sensitizes to cold temperature

Cloning of the capsaicin receptor From: Caterina, M.J., et al. Nature 389, (1997). 2:4 x 10 6 independent bacterial clones were divided into 144 pools.

TRPV1 integrates pain producing stimuli From: Tominaga, M., et al. Neuron 21, (1998).

TRPV1 KO mouse From: Caterina, M.J., et al. Science 288, (2000).

Cloning of the cold menthol receptor: TRPM8 From: McKemy, D.D., et al. Nature 416, (2002). From: Peier, A.M., et al. Cell 108, (2002).

Heat sensitive TRP channels From: Jordt, S.E., et al. Curr. Opin. Neurobiol. 13, (2003).

TRPV4 is a mechanosensor From: Liedtke,W., et al. Cell 103, (2000). TRPV4 -/- mice have impaired osmoregulation and pressure sensation

Epithelial calcium channels From: Hoenderop, J.G., et al. Physiol Rev. 85, (2005).

TRPV5-6 Biophysical properties TRPV5 From: Hoenderop, J.G., et al. Physiol Rev. 85, (2005).

The TRPV5 Knockout mouse From: Hoenderop, J.G., et al. J. Clin. Invest 112, (2003).

The TRPV (Vanilloid) family The first cloned member (1997): capsaicin receptor (TRPV1)  ”heat” receptor, “chili pepper” TRPV2-3 also temperature receptors –(insensitive to capsaicin) TRPV4 osmosensor (also temperature sensitive) TRPV5-6 Epithelial calcium transporters (only Ca 2+ selective TRP-s)

The TRPM (Melastain) family Melastatin TRPM1  tumor suppressor TRPM2  ADP ribose activated Ca 2+ permeable channel TRPM3 TRPM4  Ca 2+ activated non selective TRPM5  taste tissues TRPM6  Mg 2+ homeostasis, disease !! TRPM7  Mg 2+ homeostasis, PIP 2 activates TRPM8  Cold receptor

Some TRPM channels are also enzymes From: Yamaguchi, H., et al. Mol. Cell 7, (2001).From: Fleig, A. & Penner, R. Trends Pharmacol. Sci. 25, (2004). Kinase Domain

From: Walder, R.Y., et al. Nat. Genet. 31, (2002). Hypomagnesemia, hypocalcemia, Seizures Caused by impaired intestinal Mg 2+ absorption abnormal renal Mg 2+ excretion Can be overcome by high-dose Mg 2+ supplementation

From: Chubanov,V., et al. Proc. Natl. Acad. Sci. U. S. A 101, (2004).

Is there anything common among the regulation of TRP channels ?

From: Runnels, L.W., et al. Nat. Cell Biol. 4, (2002).

TRPM8 From: Rohacs, T., et al. Nature Neuroscience in press

The role of the TRP domain as a PIP 2 interacting site From: Rohacs, T., et al. Nature Neuroscience in press

Extended TRP superfamily From: Montell, C., et al. Mol. Cell 9, (2002). From: Clapham, D.E. Nature 426, (2003).

Another cold receptor: ANKTM1 (TRPA1) From: Story, G.M., et al. Cell 112, (2003). From: Jordt, S.E., et al. Nature 427, (2004).

Mechano-sensitive channels and hearing From: Frolenkov, G.I., et al. Nat. Rev. Genet. 5, (2004).

From: Corey, D.P., et al. Nature 432, (2004). SiRNA TRPA

From: Wilson, P.D. N. Engl. J. Med. 350, (2004). From: Igarashi, P. & Somlo, S. J. Am. Soc. Nephrol. 13, (2002). Polycystic Kidney Disease