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:

Ca10(PO4)6(OH)2

Calcium signaling

From: Clapham, D.E., et al.Nat. Rev. Neurosci. 2, 387-396 (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) Ca2+ entry (Putney)

From: Putney, J.W., Jr. Cell Calcium 11, 611-624 (1990).

Calcium Release Activated Calcium current (ICRAC)

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

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

Invertebrate Phototransduction

• Transient Receptor Potential

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

TRP channels and capacitative calcium entry

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

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

+thapsigargin

ICRAC and TRP channels

ICRAC TRPCa2+ selective Non selective

cation channel

Inwardly rectifying Outwardly rectifying

Very small single channel conductance

Measurable single channel conductance

Store depletion activates

Store depletion activates (sometimes)

Direct activation of TRP channels by the IP3 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).

PIP2 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– IP3 receptor direct interaction– PIP2 inhibits TRPL channels, other TRPC-s are not

tested yet

• No general paradigm on how PLC activates these TRPC channels

Thermosensation

HotCold

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, 816-824 (1997).

2:4 x 106 independent bacterial clones were divided into 144 pools.

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 (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 Ca2+ selective TRP-s)

The TRPM (Melastain) family

• Melastatin TRPM1 tumor suppressor• TRPM2 ADP ribose activated Ca2+ permeable

channel• TRPM3• TRPM4 Ca2+ activated non selective• TRPM5 taste tissues • TRPM6 Mg2+ homeostasis, disease !!• TRPM7 Mg2+ homeostasis, PIP2 activates• TRPM8 Cold receptor

Some TRPM channels are also enzymes

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

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

Kinase Domain

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

Hypomagnesemia, hypocalcemia, Seizures

Caused by impaired intestinal Mg2+ absorption abnormal renal Mg2+ excretion

Can be overcome by high-dose Mg2+ 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 PIP2 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

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

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

From: Igarashi, P. & Somlo, S. J. Am. Soc. Nephrol. 13, 2384-2398 (2002).

Polycystic Kidney Disease