Report on Developments Relating to State and Regional Conferences

Loomis, Ralph A.

doi:10.2307/40224485

Cited by 2 publications

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“…A very different situation exists for the lysosomal enzyme ␣-mannosidase. It also increases steadily during the same period of development (40), and this is confirmed in Fig. 6B.…”

Section: Primary Subcellular Fractionation Of Prespore Cells-earlysupporting

confidence: 71%

The Prespore Vesicles of Dictyostelium discoideum

Srinivasan¹,

Alexander

1999

Journal of Biological Chemistry

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The coordinate fusion of the prespore vesicles (PSVs) with the plasma membrane at the terminal stage of spore differentiation in Dictyostelium discoideum is an important example of developmentally regulated protein secretion. However, little is known about the composition of the vesicles, the molecular signals regulating secretion, or the mechanics of the membrane fusion. Taking a biochemical approach, we purified PSVs from different developmental stages. These preparations are highly enriched for their specific cargo of spore coat proteins while devoid of markers for other cellular compartments. Electron microscopic observations show that the PSV preparations are homogenous, with the soluble spore coat protein PsB/SP85 distributed throughout the lumen and the acid mucopolysaccharide localized in the central core. Virtually all cells secrete specific proteins that function in a variety of cellular processes, including cell-substrate interactions and intercellular signaling. In certain cell types protein secretion is constitutive, as in the case of pancreatic beta cells where secretion of insulin is the main cellular event, and the mechanics of the process are now quite well understood (1). In other cell types, such as neurons, protein secretion is regulated in a spatial and temporal pattern (2). Certainly protein secretion also plays important roles in specific events in multicellular development, although this has received much less attention. This is primarily due to the difficulty in identifying and characterizing these processes within the tissues of complex embryos. A dramatic case of developmentally regulated secretion occurs at the terminal stage of spore cell differentiation in the cellular slime mold Dictyostelium discoideum (3), and the relative simplicity of morphogenesis in this organism allows for the in depth analysis of the mechanisms that underlie this cellular event.As long as there is a source of food, Dictyostelium amoebae remain as single cells and divide by mitosis. When the food source is exhausted or removed, the cells form multicellular aggregates of approximately 10 5 cells. These multicellular aggregates then undergo a program of cytodifferentiation and morphogenesis to produce an intermediate slug and ultimately a mature fruiting body with a cellular stalk that supports about 80,000 mature spores. Proper cell differentiation results in environmentally resistant spores that are an evolutionary advantage to the organism, as they allow cells to remain viable for extended periods of time. A complex and well studied program of gene expression underlies the process of cell differentiation (4, 5).The slug stage of development shows a clear spatial distribution of cells. The cells that are destined to differentiate into spores are called prespore cells and comprise the rear 80% of the multicellular slug. The prestalk cells, destined to become stalk cells, reside in the anterior end of the slug. Prespore cells in the slug are characterized by the presence of specialized, cell type-specific secr...

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“…A very different situation exists for the lysosomal enzyme ␣-mannosidase. It also increases steadily during the same period of development (40), and this is confirmed in Fig. 6B.…”

Section: Primary Subcellular Fractionation Of Prespore Cells-earlysupporting

confidence: 71%

The Prespore Vesicles of Dictyostelium discoideum

Srinivasan¹,

Alexander

1999

Journal of Biological Chemistry

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“…Others are assayed with synthetic substrates and their natural substrates remain largely unknown. Most notable in the latter group are N-acetylglucosaminidase (Loomis, 1969b) and oc-mannosidase (Loomis, 1970) which are often used as 'markers' of early development (Fig. 3).…”

Section: Developmentally Regulated Enzymesmentioning

confidence: 99%

Protein synthesis during development and differentiation in the cellular slime mould Dictyostelium discoideum

Watts¹

1984

Biochemical Journal

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Report on Developments Relating to State and Regional Conferences

Cited by 2 publications

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The Prespore Vesicles of Dictyostelium discoideum

The Prespore Vesicles of Dictyostelium discoideum

Protein synthesis during development and differentiation in the cellular slime mould Dictyostelium discoideum

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