University:
Amherst College
Course:
CHEM 330 | Biochemical Principles of Life at the Molecular Level
Academic year:

2009
Views:

99

Pages:

16
Author:

as2st98t

Chemical Biology 03 Nov 3, 2010 Cell Communication and Signals A cell’s behavior is constantly regulated by extracellular signals: Signals: from environment or from other cells proteins peptides amino acids nucleotides steroids fatty acid derivatives dissolved gases Signaling from cell to cell = Cell Communication Signaling Cell delivers signal Receiving Cell responds to signal Receptor protein specifically recognizes signal 4 different ways in which cell signals can be delivered: 1) Paracrine Signaling signal diffuses through extracellular fluid/matrix if the signaling cell also makes receptor for that signal....? “ autocrine signaling “ 4 different ways in which cell signals can be delivered: 2) Endocrine Signaling signal travels through blood system to reach distant target cells examples: pancreatic endocrine cells secrete insulin travels through blood: affects muscle cells, liver cells, etc. kidney cells secrete erythropoietin (EPO): affects bone marrow testes and ovaries secrete steroid hormones: affect many different cells throughout the body 4 different ways in which cell signals can be delivered: 3) Contact-Dependent Signaling signal is not secreted; presented on surface of signaling cell, anchored in membrane 4 different ways in which cell signals can be delivered: 4) Neuronal Signaling electrical pulse travels very quickly down long axons to stimulate release of extracellular signal Cell-surface receptor proteins play a critical role in identifying target cells EPO EPO receptor expressed by erythrocyte progenitor only erythrocyte progenitor cells are induced to proliferate Signal Transduction: extracellular signal is converted into an intracellular signal = cell’s response to the signal Signal Transduction example: EPO hormone Players: EPO (erythropoietin) protein hormone EPO receptor (spans cell membrane) JAK protein (Janus Kinase) (“kinase” = enzyme that can add a phosphate group to amino acids tyr, ser, or thr) EPO Signal Transduction example: EPO hormone Another Player: Transcriptional Regulator called “STAT” (Signal Transducer and Activator of Transcription) EPO free to enter nucleus, and... inactive until: 1)phosphorylated 2)dimerizes 3)moves to nucleus Signal Transduction example: EPO hormone EPO BINDING OF EPO RECEPTOR EPO RESPONSE Jak-Stat signal transduction pathways are used in many different incidences always starts with an extracellular signal and ends with transcriptional activation of specific group of target genes low O2 kidney cell HIF1 Transcription Regulator is activated target genes turned on ex. EPO EPO bone marrow cells JAK-STAT signal transduction differentiated erythrocyte (RBC genes turned on) Variety of cell responses; some fast, some slow Ramifications of receiving a signal

Chemical Biology 03 Blood Biomolecular Structure IV. Nucleic Acids

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