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

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) From: Clapham, D.E., et al.

Nat. Rev. Neurosci. 2 , 387-396 (2001).

Capacitative (store operated) Ca 2+ entry (Putney) From: Putney, J.W., Jr. Cell Calcium 11 , 611-624 (1990).

C

alcium

R

elease

A

ctivated

C

alcium current (I CRAC ) From: Hoth, M. & Penner, R. Nature 355 , 353-356 (1992).

Invertebrate Phototransduction

From: Minke, B. & Cook, B. Physiol Rev. 82 , 429-472 (2002).

• Transient Receptor Potential From: Minke, B. & Cook, B. Physiol Rev. 82 , 429-472 (2002).

TRP channels and capacitative calcium entry

+thapsigargin From: Vaca, L., et al. Am. J. Physiol. 267 C1501-C1505 (1994).

From: Zhu, X., et al. Cell 85 , 661-671 (1996).

I

CRAC

and TRP channels

I CRAC Ca 2+ selective Inwardly rectifying Very small single channel conductance Store depletion activates TRP Non selective cation channel Outwardly rectifying Measurable single channel conductance Store depletion activates (sometimes)

Direct activation of TRP channels by the IP

3

receptor

From: Kiselyov, K., et al. Nature 396 , 478-482 (1998).

DAG activation of TRPC3,6,7

From: Hofmann,T., et al. Nature 397 , 259-263 (1999).

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

The TRPC (

C

lassical) 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

Capsaicin (chili pepper) sensitizes to warm temperature Menthol sensitizes to cold temperature

Hot Cold

Cloning of the capsaicin receptor 2:4 x 10 6 independent bacterial clones were divided into 144 pools.

From: Caterina, M.J., et al. Nature 389 , 816-824 (1997).

TRPV1 integrates pain producing stimuli From: Tominaga, M., et al. Neuron 21 , 531-543 (1998).

TRPV1 KO mouse From: Caterina, M.J., et al. Science 288 , 306-313 (2000).

Cloning of the cold menthol receptor: TRPM8 From: McKemy, D.D., et al. Nature 416 , 52-58 (2002).

From: Peier, A.M.

,

et al . Cell 108 , 705-715 (2002).

Heat sensitive TRP channels From: Jordt, S.E., et al. Curr. Opin. Neurobiol. 13 , 487-492 (2003).

TRPV4 is a mechanosensor

From: Liedtke,W., et al. Cell 103 , 525-535 (2000).

TRPV4 -/- mice have impaired osmoregulation and pressure sensation

Epithelial calcium channels

From: Hoenderop, J.G., et al. Physiol Rev. 85 , 373-422 (2005).

TRPV5-6 Biophysical properties

TRPV5 From: Hoenderop, J.G., et al. Physiol Rev. 85 , 373-422 (2005).

The TRPV5 Knockout mouse From: Hoenderop, J.G., et al. J. Clin. Invest 112 , 1906-1914 (2003).

The TRPV (

V

anilloid) 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 (

M

elastain) family

• Melastatin TRPM1  • TRPM2  channel tumor suppressor ADP ribose activated Ca 2+ permeable • TRPM3 • TRPM4  • TRPM5  Ca 2+ activated non selective taste tissues • TRPM6  • TRPM7  • TRPM8  Mg Mg 2+ 2+ homeostasis, disease !!

homeostasis, PIP Cold receptor 2 activates

Some TRPM channels are also enzymes

K

inase

D

omain From: Fleig, A. & Penner, R. Trends Pharmacol. Sci. 25 , 633 639 (2004).

From: Yamaguchi, H., et al. Mol. Cell 7 , 1047-1057 (2001).

From: Walder, R.Y., et al. Nat. Genet. 31 , 171-174 (2002).

Hypomagnesemia, hypocalcemia, Seizures Caused by impaired intestinal Mg 2+ abnormal renal Mg 2+ excretion absorption Can be overcome by high-dose Mg 2+ supplementation

From: Chubanov,V., et al. Proc. Natl. Acad. Sci. U. S. A 101 , 2894-2899 (2004).

Is there anything common among the regulation of TRP channels ?

From: Runnels, L.W., et al. Nat. Cell Biol. 4 , 329-336 (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 , 229-231 (2002).

From: Clapham, D.E. Nature 426 , 517-524 (2003).

Another cold receptor: ANKTM1 (TRPA1) From: Story, G.M., et al. Cell 112 , 819-829 (2003). From: Jordt, S.E., et al. Nature 427 , 260-265 (2004).

Mechano-sensitive channels and hearing From: Frolenkov, G.I., et al. Nat. Rev. Genet. 5 , 489-498 (2004).

From: Corey, D.P., et al. Nature 432 , 723-730 (2004). SiRNA TRPA

Polycystic Kidney Disease http://peir.path.uab.edu/iplab/messages/598/467.html?1002303218

From: Igarashi, P. & Somlo, S.

J. Am. Soc. Nephrol.

13

, 2384-2398 (2002).

From: Wilson, P.D. N. Engl. J. Med. 350 , 151-164 (2004).