Signal Transduction

General Cell Signaling

BioCarta: Pathways - "Interactive graphic models of molecular and cellular pathways."
Biochemistry Online: An Approach Based on Chemical Logic - Biochemistry within the framework of chemical principles and logic. (Henry Jakubowski, College of St. Benedict/St. John's University)
Cell Science at a Glance - "Signalling pathways, phylogenetic trees, multiprotein complexes, useful reagents – and much more – summarized in a single figure." (Journal of Cell Science)
Cell Signaling Pathway Slides and Charts (Sigma-Aldrich)
NPG Web Focus: Kinases in Cancer - "The Focus examines the role of kinase signalling in cancer and the potential for developing effective therapies that can modulate various kinase pathways." (Nature Publishing Group)
Inositols.com - Resources covering the following areas: inositols, phosphoinositides, phospholipids, lipid kinases, cell signaling, inhibitors, calcium metabolism and other related topics. (A.G. Scientific)
The Interactive Fly: Evolutionarily Conserved Pathways (Society for Developmental Biology). Includes sections on:
- Ca²⁺-Binding Proteins and Dependent Pathways - "Conserved systems responsive to the level of Ca²⁺ ion in the cell."
- Cell Survival - "Epidermal Growth Factor (EGF) and its receptor, the Ras pathway and ETS transcription factors."
- Dorsal-Ventral Polarity - "Decapentaplegic and Bone Morphogenic Proteins (BMPs), including their interacting proteins, receptors and downstream targets."
- Ectoderm/Mesoderm Interaction - "Ectodermal Fibroblast Growth Factor (FGF) involvement in development of respiratory and muscle systems."
- Lateral Inhibition - "The Notch pathway."
- The Learning Pathway - "Cyclic AMP second messenger system."
- Molting and the Response to Small Hydrophobic Hormones - "The steroid receptor superfamily."
- Proneural Pathway - "Achaete-Scute homologs and interacting proteins."
- Segment Polarity - "Hedgehog and its targets are phylogenetically conserved."
- Stress Activated and Cell Motility Feedback Pathway - "The Jun-N-terminal kinase (JNK) activated MAP kinase cascade links the Rho family of GTP-binding proteins to transcription of Jun."
- Tissue Patterning and Boundary Formation - "A role for Fringe in modulating Notch signaling."
Kimball's Biology Pages - A comprehensive online biology textbook. (Beginner's Level)
- Cell Signaling - Basic overview of cell signaling.
- Oncogenes - Tutorial on oncogenes, the cancer-promoting form of positive growth control genes.
- Tumor Suppressor Genes - Tutorial on tumor suppressor genes (anti-oncogenes).
The Medical Biochemistry Page - An excellent biochemistry tutorial with information on a broad range of biochemical pathways. (Michael W. King, Terre Haute Center for Medical Education, Indiana University School of Medicine)
Regulators of Signal Transduction Pathways - Information on transforming growth factor β (TGF-β), Wnt, Janus kinase/signal transducer and activator of transcription (JAK/STAT), Smad, adenomatous polyposis coli (APC)/β-catenin, lipid and other signaling pathways.
Signaling Gateway - Cell signaling research, news, data and conferences. (Alliance for Cellular Signaling and Nature Publishing Group)
Signal Transduction Knowledge Environment - Resources and information on signal transduction; an electronic journal with perspectives and reviews. (Science and Stanford University)
Wikipedia - Free online encyclopedia with basic overviews. (Beginner's Level)

General Signal Transduction Databases (Data Collections on Regulatory Pathways)

Biological Biochemical Image Database - Images of biological pathways, macromolecular structures, gene families and cellular relationships. (National Institute of Aging)
Database of Quantitative Cellular Signaling - "The Database of Quantitative Cellular Signaling is a repository of models of signaling pathways." (National Centre for Biological Science, India)
Dynamic Signaling Maps - "A Web-based software suite that allows scientists and biomedical research organizations to integrate, analyze, manipulate, and visualize biological signaling pathways and protein-protein interaction data." (Hippron Physiomics)
Kyoto Encyclopedia of Genes and Genomes (KEGG) - Graphical and hypertext-based information on biochemical pathways, including metabolic and regulatory pathways (for instance, cell cycle and growth factor signaling).
The Signaling Pathway Database (SPAD) - Database with diagrams of cell signaling pathways.

Also see the Databases and Simulations section of the Systems Biology page. For specific signaling protein and pathway databases, see below.

Signaling Ligands: Growth Factors, Cytokines, Trophic Factors, Hormones and Neurotransmitters

Cytokines Online Pathfinder Encyclopaedia (COPE) - Extensive informational site on cytokines, chemokines and receptors, with detailed descriptions of thousands of relevant proteins and cell types. (Horst Ibelgaufts)
The Cytokines Web - Information about cytokines and their receptors that "provides leading-edge scientific information about cytokines and their receptors, including 3-D structural information and topological and evolutionary relationships. It also contains information about potential theraputic uses for some human cytokines."
Cytokine Signaling Pathway Database - "[D]esigned to be a tool for biomedical researchers who work with cytokines and their receptors, and provides biochemical data and references about signaling molecules as well as ligand-receptor relationships."
The Growth Factor and Cytokine Page - Information on growth factors and cytokines.
Neurotransmitter.net - This is "a non-commercial project with an open-ended mission to educate and innovate in the fields of neuroscience, psychology, and pharmacology."
Neurotrophic Factors - A collection of pages relating to the structures of neurotrophic factors.

Receptors

The G-Protein-Coupled Receptor Database (GCRDb) - Database on G-protein-coupled receptors.
The Glococoricoid Receptor Resource - "The Glucocorticoid Receptor Resource is currently a collection of facts on the GR, sources for clones and antibodies, maps/sequences of GR expression vectors, and phenotypes of mutations." (Georgetown University)
GRAP Mutant Database - Database on G-protein-coupled receptors and their mutants.
MIT Biology Hypertextbook: Receptors - Tutorial on transmembrane receptors and signaling cascades. (Beginner's Level)
The Nuclear Receptor Resource - A collection of individual databases on members of the steroid and thyroid hormone receptor superfamily (such as glucocorticoid, androgen, thyroid hormone and mineralocorticoid receptors). (Georgetown University)
NURSA - Nuclear Receptor Signaling Atlas - "The primary directive of our NURSA program is to gather and organize information relating to key aspects of orphan nuclear receptor biology, with the aim of extending this blueprint to the wider discipline of nuclear receptor signaling." (Co-Directors: Bert W. O'Malley, Baylor College of Medicine; Ronald M. Evans, Salk Institute for Biological Studies)
The Olfactory Receptor Database (ORDB) - Database that "aims to house all of the known olfactory receptor and chemoreceptor sequences in both nucleotide and amino acid form." (Yale University)

Kinases

Kinase.com - A "protein kinase gene resource. This site contains analyses of protein kinases from humans and model organisms (yeast, worm and fly), carried out by researchers at Sugen, Evolutionary Bioinformatics, and the Salk Institute."
- KinBase
- Kinome Projects
- Protein Kinase Evolution
Kinase Pathway Database - An "integrated database concerning completed sequenced major eukaryotes, which contains the classification of protein kinases and their functional conservation and orthologous tables among species, protein-protein interaction data, domain information, structural information, and automatic pathway graph image interface."
Kinase Substrate Database - Database of published substrates for a broad range of kinases. (Kinasource)
The Protein Kinase Resource - A compendium of information on protein kinases.
Protein Kinase Resources - General resource with links to relevant recent literature, news and job listings. (Ion Channel Media Group)

Other Signaling Molecules

The Calpain Family of Proteases - Information on calpains, calcium-dependent cytosolic proteases involved in signal transduction.
Cyclic GMP Site - Resources on the nitric oxide/cyclic GMP signaling pathway with diagrams, animations and links.
The EF-Hand Calcium-Binding Proteins Data Library - "A growing collection of published sequence, structural, functional, and other information about EF-hand calcium-binding proteins and their roles in cellular signal transduction." (Melanie Nelson, Physiome Sciences)

Specific Signaling Pathways

Hedgehog Signaling Pathway Database - Bioinformatic resources and annotations for the Hedgehog signaling pathway. (F.A. Ramirez-Weber, San Francisco State University)
Mammalian MAPK Signalling Pathways - Image map depicting major components of MAPK pathways. (Jim Woodgett, University of Toronto, Canada)
Synaptic Transmission: A Four-Step Process - A multimedia (text, images and animations) introduction to the basic steps in synaptic transmission. (Multimedia Neuroscience Education Project)
The Yeast Pheromone Signal Transduction Pathway - Image map with links to relevant references. (Lab of David Thomas, NRC Biotechnology Research Institute, Canada)