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L19 2009 Multicellular signalling

L19 2009 Multicellular signalling - MULTICELLULARITY CELL...

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MULTICELLULARITY: CELL SIGNALING Lecture 19 9 October 2009 Multicellularity: Cell diversification acellular slime molds aggregation akinete boundary layer budding cellular slime molds cheaters chemotaxis Chlamydomonas cyanobacteria cyclic adenosine monophosphate (cAMP) Dictyostelium dispersal ability division of labor Eudorina fruiting body functional differentiation germ cells Gonium heterocyst incomplete cytokinesis Myxobacteria nitrogen fixation Pandorina pleuripotent signaling proteins somatic cells soma spores stalk surface area-to-volume ratio vegetative cells Volvocales Volvox Costs of multicellularity 1. competition 2. reduced fitness - cheaters 3. distribution of nutrients 4. signalling, coordination
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Differentiation of cells requires 1. complex development pleuripotency. A cell has the ability to differentiate into many different types of cell 2. chemical signalling for coordination Nostoc sp. H Synechocystis sp. Close relatives, genomes 80%- 90% identical Signal ing proteins: 3200 versus 7400 Where we’re going 1. signals – local, global 2. reception – membrane, intracellular 3. transduction cascades 4. cellular responses – fast, slow Local signaling without secretion Nostoc sp. H Local signaling with secretion Paracrine signaling secretions of one cell change growth or development of target cells Synaptic transmission neurotransmitter released by nerve terminal causes muscle contraction or nerve-nerve signaling. Presynaptic nerve cell Postsynaptic cell synaptic cleft Global, long distance signaling endocrine signaling, hormones • Endocrine gland releases hormone into blood system • Target cell has hormone receptors on cell membrane or intracellular Effect of epinephrine on cells in liver and muscle Earl Sutherland,
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L19 2009 Multicellular signalling - MULTICELLULARITY CELL...

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