Role of the C-terminal SH3 domain and N-terminal tyrosine phosphorylation in regulation of Tim and related Dbl-family proteins

Biochemistry. 2008 Jul 1;47(26):6827-39. doi: 10.1021/bi702543p. Epub 2008 Jun 7.

Abstract

Dbl-related oncoproteins are guanine nucleotide exchange factors (GEFs) specific for Rho-family GTPases and typically possess tandem Dbl (DH) and pleckstrin homology (PH) domains that act in concert to catalyze exchange. Although the exchange potential of many Dbl-family proteins is constitutively activated by truncation, the precise mechanisms of regulation for many Dbl-family proteins are unknown. Tim and Vav are distantly related Dbl-family proteins that are similarly regulated; their Dbl homology (DH) domains interact with N-terminal helices to exclude and prevent activation of Rho GTPases. Phosphorylation, substitution, or deletion of the blocking helices relieves this autoinhibition. Here we show that two other Dbl-family proteins, Ngef and Wgef, which like Tim contain a C-terminal SH3 domain, are also activated by tyrosine phosphorylation of a blocking helix. Consequently, basal autoinhibition of DH domains by direct steric exclusion using short N-terminal helices likely represents a conserved mechanism of regulation for the large family of Dbl-related proteins. N-Terminal truncation or phosphorylation of many other Dbl-family GEFs leads to their activation; similar autoinhibition mechanisms could explain some of these events. In addition, we show that the C-terminal SH3 domain binding to a polyproline region N-terminal to the DH domain of the Tim subgroup of Dbl-family proteins provides a unique mechanism of regulated autoinhibition of exchange activity that is functionally linked to the interactions between the autoinhibitory helix and the DH domain.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Sequence
  • Animals
  • COS Cells
  • Cell Cycle Proteins / chemistry*
  • Cell Cycle Proteins / classification
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Chlorocebus aethiops
  • GTP Phosphohydrolases / chemistry
  • GTP Phosphohydrolases / metabolism
  • Guanine Nucleotide Exchange Factors / chemistry*
  • Guanine Nucleotide Exchange Factors / classification
  • Guanine Nucleotide Exchange Factors / genetics
  • Guanine Nucleotide Exchange Factors / metabolism*
  • Humans
  • Intracellular Signaling Peptides and Proteins / chemistry*
  • Intracellular Signaling Peptides and Proteins / classification
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Molecular Sequence Data
  • Mutation / genetics
  • Phosphorylation
  • Phosphotyrosine / metabolism*
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • src Homology Domains*
  • src-Family Kinases / metabolism

Substances

  • Cell Cycle Proteins
  • Guanine Nucleotide Exchange Factors
  • Intracellular Signaling Peptides and Proteins
  • TIMELESS protein, human
  • Phosphotyrosine
  • src-Family Kinases
  • GTP Phosphohydrolases