Cells communicate through signaling molecules that are detected by receptors on other cells. Signals are transmitted across the cell membrane by signal transduction pathways and cause changes in cell function. Signals may target nearby (paracrine), distant (endocrine), or adjacent (juxtacrine) cells. Ion channels in the cell membrane are important for signal transduction and are classified by their method of gating, such as ligand-gated channels that open in response to neurotransmitters.

1. PRESENTED BY
V.Prem Prasad
M.Pharmacy 1stYear(pharmacology)
Gokaraju rangaraju college of pharmacy 1

2. CONTENTS
 Introduction
 Modes of cell signaling
 Communication between cells
 Signal transduction
 Ion channels
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3. INTRODUCTION:
Cells must be ready to respond to essential signals in their environment. These
are often chemicals in the extracellular fluid (ECF) from:
distant locations - signaling by hormones;
nearby cells  cytokines;
or
even secreted by themselves .
Long-range allostery is often a significant component of cell signaling events.
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4. CELL SIGNALING
Cell signaling is part of a complex system of communication that governs basic
cellular activities and coordinates cell actions.
The ability of cells to perceive and correctly respond to their microenvironment is the
basis of development, tissue repair, and immunity as well as normal tissue homeostasis
Errors in cellular information processing are responsible for diseases such as cancer,
autoimmunity, and diabetes. By understanding cell signaling, diseases may be treated
effectively and, theoretically, artificial tissues may be created.
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6. CELL SIGNALING & SIGNAL
TRANSDUCTTION
 Why do cells communicate
 How are signals transmitted between cells
 How are signals transmitted across cell membranes
into cell interior
 How are signals transmitted within a cell
 How do signals affect a cell function
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9. STEPS IN CELL SIGNALING
SYNTHESIS OF SIGNALLING
MOLECULES
RELEASE OF SIGNALLING MOLECULES
TRANSPORT OF SIGNAL TO TARGET
CELLS
DETECTION & BINDING OF SIGNAL BY SPECIFIC RECEPTOR
CHANGES DUE TO RECEPTOR-SIGNAL COMPLEX
SIGNAL REMOVAL &
RESPNOSE TERMINATION 9

10. CLASSIFICATION OF INTERCELLULAR
COMMUNICATION
Intercellular signaling is subdivided into the following classifications:
Autocrine signals target the cell itself. Sometimes autocrine cells can target cells
close by if they are the same type of cell as the emitting cell. An example of this are
immune cells.
Paracrine signals target cells in the vicinity of the emitting cell. neurotransmitters
represent an example.
Endocrine signals target distant cells. Endocrine cells produce hormones that travel
through the blood to reach all parts of the body.
Juxtacrine signals target adjacent (touching) cells. These signals are transmitted
along cell membranes via protein or lipid components integral to the membrane and are
capable of affecting either the emitting cell or cells immediately adjacent.
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14. JUXTACRINE SIGNALING
MEMBRANE-ANCHORED
LIGANDS
e.g.*Notch signalling.
NEIGHBOURING
CELLS
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31. Ion Channels
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32. Schematic diagram of an ion channel
1 - Channel domains(typically
four per channel),
2 - Outer vestibule,
3 - Selectivity filter,
4 - Diameter of selectivity filter,
5 - Phosphorylation site,
6 - Cell membrane.
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33. Cell membrane
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34. Membrane transport proteins
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35. Ion channels are not pumps
Only ion channels have an aqueous pore that crosses the
membrane
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36. Channels are made up of subunits
 Ion channels are made from 2-6 similar proteins or homologous
structural units ‐ PORE-FORMING SUBUNITS - they associate creating
the functional ion channel
 In addition, many channels contain the auxiliary regulatory subunits
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37. Channels are made up of subunits
 Pore-forming subunits contain an α‐helix made by ~20 hydrophobic
amino acids which interact with the annular phospholipids of the lipid
bilayer
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38. Ion channel types (by gating)
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39. Ligand-gated channels
Typically, these are ion channels located on the postsynaptic
(receiving) side of the neuron
Some act in response to a secreted (external) ligand- typically a
neurotransmitter such as
• Acetylcholine (ACh)
• GABA
• Glycine
• Glutamate
Some act in response to internal ligands such as G-proteins,
cGMP and cAMP, and are also regulated by internal metabolites
such as phosphoinositides, arachidonic acid, calcium.
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40. Signal-gated channels
Atrial m2 receptor-G protein-
coupled K+ channels
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41. Modifiers of Channel Gating
(curare)
(alpha-
bungarotoxin)
(ACh)
Binding of exogenous ligands
can block gating
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42. Modifiers of Channel Gating
Ion permeation can be
prevented by pore blockers,
e.g. voltage-dependent
block of NMDARs by Mg2+
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43. Modifiers of Channel Gating
Current
Time
Open
Closed
Open
Closed
Exogenous modulators can modify the action of endogenous ligands
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44. Bu Z, Callaway DJ (2011). "Proteins MOVE! Protein dynamics and long-range allostery
in cell signaling". Advances in Protein Chemistry and Structural Biology . Advances in
Protein Chemistry and Structural Biology 83 : 163–221.
Rang & Dale's Pharmacology
http://en.wikipedia.org/wiki/Cell_signaling
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CellSignaling.html
www.authorstream.com/.../shona6685-645587-ppt -cell -signaling
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC151254/
 Congreve M, Marshall F (March 2010). "The impact of GPCR structures on
pharmacology and structure-based drug design". Br. J. Pharmacol. 159 (5): 986–
96.doi:10.1111/j.1476-5381.2009.00476x PMC 2839258 PMID19912230
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