A cell number-counting factor regulates levels of a novel protein, SslA, as part of a group size regulation mechanism in Dictyostelium

Tong Gao, Celine Roisin-Bouffay, R. Diane Hatton, Lei Tang, Debra A. Brock, Tiffany DeShazo, Laura Olson, Wan Pyo Hong, Wonhee Jang, Elvia Canseco, Deenadayalan Bakthavatsalam, Richard H. Gomer

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Developing Dictyostelium cells form aggregation streams that break into groups of ∼2 × 104 cells. The breakup and subsequent group size are regulated by a secreted multisubunit counting factor (CF). To elucidate how CF regulates group size, we isolated second-site suppressors of smlA -, a transformant that forms small groups due to oversecretion of CF. smlA- sslA1(CR11) cells form roughly wild-type-size groups due to an insertion in the beginning of the coding region of sslA1, one of two highly similar genes encoding a novel protein. The insertion increases levels of SslA. In wild-type cells, the sslA1 (CR11) mutation forms abnormally large groups. Reducing SslA levels by antisense causes the formation of smaller groups. The sslA(CR11) mutation does not affect the extracellular accumulation of CF activity or the CF components countin and CF50, suggesting that SslA does not regulate CF secretion. However, CF represses levels of SslA. Wild-type cells starved in the presence of smlA- cells, recombinant countin, or recombinant CF50 form smaller groups, whereas sslA1(CR11) cells appear to be insensitive to the presence of smlA- cells, countin, or CF50, suggesting that the sslA1(CR11) insertion affects CF signal transduction. We previously found that CF reduces intracellular glucose levels. sslA(CR11) does not significantly affect glucose levels, while glucose increases SslA levels. Together, the data suggest that SslA is a novel protein involved in part of a signal transduction pathway regulating group size.

Original languageEnglish
Pages (from-to)1538-1551
Number of pages14
JournalEukaryotic Cell
Volume6
Issue number9
DOIs
StatePublished - Sep 2007

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