Intermediate filaments (IFs) continuously exchange between a small, depolymerized fraction of IF protein and fully polymerized IFs. To elucidate the possible role of phosphorylation in regulating this equilibrium, we disrupted the exchange of phosphate groups by specific inhibition of dephosphorylation and by specific phosphorylation and site-directed mutagenesis of two of the major in vivo pho...

The chemokine receptor CXCR4 is a widely expressed G protein-coupled receptor that has been implicated in a number of diseases including human immunodeficiency virus, cancer, and WHIM syndrome, with the latter two involving dysregulation of CXCR4 signaling. To better understand the role of phosphorylation in regulating CXCR4 signaling, tandem mass spectrometry and phospho-specific antibodies we...

Ribosomal S6 kinase 1 (S6K1), as a key regulator of mRNA translation, plays an important role in cell cycle progression through the G1 phase of proliferating cells and in the synaptic plasticity of terminally differentiated neurons. Activation of S6K1 involves the phosphorylation of its multiple Ser/Thr residues, including the proline-directed sites (Ser-411, Ser-418, Thr-421, and Ser-424) in t...

A protein expressed in immune cells and muscle was detected in muscle extracts as a substrate for several SAPKs (stress-activated protein kinases). It interacted specifically with the F-actin capping protein CapZ in splenocytes, and was therefore termed 'CapZIP' (CapZ-interacting protein). Human CapZIP was phosphorylated at Ser-179 and Ser-244 by MAPKAP-K2 (mitogen-activated protein kinase-acti...