Upon activation, the epidermal growth factor (EGF) receptor becomes phosphorylated and triggers a vast signaling network that has profound effects on cell growth. The EGF receptor is observed to assemble into clusters after ligand binding and tyrosine kinase autophosphorylation, but the role of these assemblies in the receptor signaling pathway remains unclear. To address this question, we meas...

Phosphorylation provides an important mechanism by which transcription factor activity is regulated. Estrogen receptor alpha (ERalpha) is phosphorylated on multiple sites, and stimulation of a number of growth factor receptors and/or protein kinases leads to ligand-independent and/or synergistic increase in transcriptional activation by ERalpha in the presence of estrogen. Here we show that ERa...

We have characterized the ligand-enhanced phosphorylation of the CXC chemokine receptor-2 (CXCR2) in a series of clonal 3ASubE cell lines expressing receptors truncated or mutated in the carboxyl-terminal domain. Truncation of CXCR2 by substitution of a stop codon for Ser-342 (342T) or Ser-331 (331T) results in total loss of melanoma growth stimulatory activity/growth-related protein (MGSA/GRO)...

The peroxisome proliferator-activated receptor-gamma (PPARgamma) transcription factor plays a pivotal role in adipocyte differentiation and metabolic regulation. The transcriptional activity of PPARgamma is positively modulated by ligand binding and negatively regulated by phosphorylation mediated by the MEK/ERK signaling pathway. The phosphorylation of mouse PPARgamma1 at Ser82 by ERK causes a...

Receptor tyrosine kinases of the Eph family become tyrosine phosphorylated and initiate signalling events upon binding of their ligands, the ephrins. Eph receptors such as EphA2 and EphB4 are highly expressed but poorly tyrosine phosphorylated in many types of cancer cells, suggesting a limited interaction with ephrin ligands. Nevertheless, decreasing the expression of these receptors affects t...

In order to investigate early signal transduction events in myeloid cells, the phosphosubstrates of an interleukin 3 (IL 3)-dependent cell line, FDC-P1, have been analyzed. Using synthetic diacylglycerol as a direct activator of the unique calcium-phospholipid-dependent phosphotransferase protein kinase C (PK-C) and genetically engineered homogeneous IL 3, we have demonstrated a common element ...

VEGFR-2 is the primary regulator of angiogenesis, the development of new blood vessels from pre-existing ones. VEGFR-2 has been hypothesized to be monomeric in the absence of bound ligand, and to undergo dimerization and activation only upon ligand binding. Using quantitative FRET and biochemical analysis, we show that VEGFR-2 forms dimers also in the absence of ligand when expressed at physiol...

The topography and functional domains of the cAMP chemotactic receptor of Dictyostelium discoideum were investigated by protease sensitivity to chymotrypsin. Proteolytic digestion of intact cells produced a 23-kDa fragment of the receptor that retained the photoaffinity label used to identify the receptor. Additionally, this fragment contained the sites phosphorylated by CAR-kinase, the enzyme ...