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Eukaryotic Cell, February 2002, p. 126-136, Vol. 1, No. 1
1535-9778/02/$04.00+0     DOI: 10.1128/EC.1.1.126-136.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

CulB, a Putative Ubiquitin Ligase Subunit, Regulates Prestalk Cell Differentiation and Morphogenesis in Dictyostelium spp.

*** Bin Wang1 and Adam Kuspa1,2*

Verna and Marrs McLean Department of Biochemistry and Molecular Biology,1 Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 770302

Received 23 January 2001/ Accepted 1 October 2001

Dictyostelium amoebae accomplish a starvation-induced developmental process by aggregating into a mound and forming a single fruiting body with terminally differentiated spores and stalk cells. culB was identified as the gene disrupted in a developmental mutant with an aberrant prestalk cell differentiation phenotype. The culB gene product appears to be a homolog of the cullin family of proteins that are known to be involved in ubiquitin-mediated protein degradation. The culB mutants form supernumerary prestalk tips atop each developing mound that result in the formation of multiple small fruiting bodies. The prestalk-specific gene ecmA is expressed precociously in culB mutants, suggesting that prestalk cell differentiation occurs earlier than normal. In addition, when culB mutant cells are mixed with wild-type cells, they display a cell-autonomous propensity to form stalk cells. Thus, CulB appears to ensure that the proper number of prestalk cells differentiate at the appropriate time in development. Activation of cyclic AMP-dependent protein kinase (PKA) by disruption of the regulatory subunit gene (pkaR) or by overexpression of the catalytic subunit gene (pkaC) enhances the prestalk/stalk cell differentiation phenotype of the culB mutant. For example, culB- pkaR- cells form stalk cells without obvious multicellular morphogenesis and are more sensitive to the prestalk O (pstO) cell inducer DIF-1. The sensitized condition of PKA activation reveals that CulB may govern prestalk cell differentiation in Dictyostelium, in part by controlling the sensitivity of cells to DIF-1, possibly by regulating the levels of one or more proteins that are rate limiting for prestalk differentiation.

* Corresponding author. Mailing address: Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Rm. T321, Houston, TX 77030. Phone: (713) 798-8278. Fax: (713) 796-9438. E-mail: akuspa{at}bcm.tmc.edu.

Eukaryotic Cell, February 2002, p. 126-136, Vol. 1, No. 1
1535-9778/02/$04.00+0     DOI: 10.1128/EC.1.1.126-136.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Good, J. R., Cabral, M., Sharma, S., Yang, J., Van Driessche, N., Shaw, C. A., Shaulsky, G., Kuspa, A. (2003). TagA, a putative serine protease/ABC transporter of Dictyostelium that is required for cell fate determination at the onset of development. Development 130: 2953-2965 [Abstract] [Full Text]  


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