14: Signal Transduction
- Page ID
- 16183
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Metazoan organisms are not just conglomerations of cells that happen to stick together. The cells each have specific functions that must be coordinated with one another in order to assure the survival of the organism and thus the shared survival of the component cells. If coordination is required, then a method of communication between cells is also required. In fact, it is even more complicated than that because the communications between the cells only scratches the surface and the intracellular communication that goes on to coordinate multiple cellular activities in response to an external signal is usually far more complex than the initial transmission of that signal.
- 14.1: Introduction to Signal Transduction
- This page describes three modes of intercellular communication: juxtacrine, where cells communicate through direct contact, exemplified by the Delta-Notch pathway; paracrine, which involves short-distance signaling using growth factors like Nerve Growth Factor (NGF) for neural cell survival; and endocrine signaling, where hormones are released into the bloodstream to influence distant cells, with effects contingent on receptor availability.
- 14.2: Receptors and Ligands
- This page discusses receptors, which are specialized proteins that bind to a variety of extracellular ligands such as gases, amino acids, lipids, and peptides, leading to intracellular signaling cascades. Unlike ligands, receptors are solely proteins and often exhibit specific binding, even though ligands can interact with numerous receptors. The binding process activates enzymes that amplify signals, which is essential for various cellular functions, including growth and movement.
- 14.3: 7-TM receptors (G-protein-coupled)
- This page discusses G-protein-coupled receptors (GPCRs), which are 7-transmembrane proteins activated by ligands such as neurotransmitters and hormones. Activation leads to conformational changes that stimulate G proteins, initiating signaling pathways. Key pathways involve adenylate cyclase, producing cAMP, and phospholipase C, generating IP3 and DAG.
- 14.4: Receptor Tyrosine Kinases
- This page discusses receptor tyrosine kinases (RTKs), highlighting their unique structure and function compared to 7-TM receptors. RTKs require dimerization for activation, leading to cross-phosphorylation that initiates the MAP kinase pathway through Ras activation, producing varied cellular responses. They play critical roles in growth and survival, with the insulin receptor exemplifying complex signaling.
- 14.5: Calcium Ion Signaling
- This page emphasizes the essential function of calcium signaling in coordinating intracellular activities, particularly in muscle contraction and fertilization. It highlights the role of calcium-binding proteins like calmodulin in activating key enzymes. The importance of nitric oxide (NO) signaling, especially in vasodilation through guanylate cyclase, is discussed, along with the impact of sildenafil (Viagra) as a PDE5 inhibitor that boosts NO signaling.
Thumbnail: Simplified representation of major signal transduction pathways in mammals. (CC BY-SA 3.0; cybertory & Roadnottaken).