אסיף מאגר המחקר החקלאי

Identification and targeted gene disruption of cAR3, a cAMP receptor subtype expressed during multicellular stages of Dictyostelium development

Year:

1993

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Volume :

7

Co-Authors:

Johnson, R.L., Department of Biological Chemistry, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, United States
Saxe III, C.L., Lab. of Cell./Developmental Biology, NIDDKD (6/B1-12), National Institutes of Health, Bethesda, MD 20892, United States, Department of Anatomy, Emory University, School of Medicine, Atlanta, GA 30322, United States
Gollop, R., Lab. of Cell./Developmental Biology, NIDDKD (6/B1-12), National Institutes of Health, Bethesda, MD 20892, United States
Kimmel, A.R., Lab. of Cell./Developmental Biology, NIDDKD (6/B1-12), National Institutes of Health, Bethesda, MD 20892, United States
Devreotes, P.N., Department of Biological Chemistry, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, United States

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Abstract:

Extracellular cAMP acts through cell-surface receptors to coordinate the developmental program of Dictyostelium. A cAMP receptor (cAR1), which is expressed during early aggregation, has been cloned and sequenced previously. We have identified a new receptor subtype, cAR3, that has ∼56% and 69% amino acid identity with cAR1 and cAR2, respectively. cAR1, cAR2, or cAR3 expressed from plasmid in growing Dictyostelium cells can be photoaffinity labeled with 8-N3[32P]cAMP and phosphorylated when stimulated with cAMP. cAR3 RNA was not present during growth but appeared during late aggregation. Its expression peaked at 9 hr and then fell to a reduced level that was maintained until culmination. The expression of cAR3 protein followed a similar pattern, but with a 3-hr lag, and reached a maximum at the mound stage. In contrast, cAR1 protein was expressed predominantly during early aggregation and at low levels during later stages. At their respective peaks of expression, there were ∼5 × 103 cAR3 sites per cell compared with ∼7 × 104 cAR1 sites per cell. The cAR3 gene was disrupted by homologous recombination in several different parental cell lines. Surprisingly, the car3- cell lines display no obvious phenotype.

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