The discovery of sequence motifs that mediate protein-protein interactions, coupled with the availability of protein amino acid sequence data, allows for the identification of putative protein binding pairs. The present studies were based on our identification of an amino acid sequence in phosphatidylinositol-specific phospholipase C-␥1 (PLC-␥1) that fits the consensus sequence for a mitogen-activated protein kinase (MAPK) binding site, termed the D-domain. Extracellular signal-regulated kinase 2 (ERK2), an MAPK, and phospho-ERK2 were bound by an immobilized peptide sequence containing the identified PLC-␥1 D-domain. Furthermore, a peptide containing the PLC-␥1 D-domain was able to competitively inhibit the in vitro phosphorylation of recombinant PLC-␥1 by recombinant phospho-ERK2, whereas a control peptide derived from a distant region of PLC-␥1 was ineffective. Similarly, the peptide containing the PLC-␥1 D-domain, but not the control peptide, competitively inhibited the in vitro phosphorylation of Elk-1 and c-Jun catalyzed by recombinant phospho-ERK2 and phospho-c-Jun N-terminal kinase 3 (phospho-JNK3), another type of MAPK, respectively. Incubation of anti-PLC-␥1 immunocomplexes isolated from rat brain with recombinant phospho-ERK2 opposed the increase in PLC-␥1-catalyzed hydrolysis of phosphatidylinositol 4,5-P 2 (PtdIns(4,5)P 2 ), which was produced by a tyrosine kinase associated with the immunocomplexes, whereas in vitro phosphorylation of recombinant PLC-␥1 by recombinant phospho-ERK2 did not alter PLC-␥1-catalyzed PtdIns(4,5)P 2 hydrolysis. These studies have uncovered a previously unidentified mechanism for the integration of PLC-␥1-and ERK2-dependent signaling.

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Background: Reversible interactions between the components of cellular signaling pathways allow for the formation and dissociation of multimolecular complexes with spatial and temporal resolution and, thus, are an important means of integrating multiple signals into a coordinated cellular response. Several mechanisms that underlie these interactions have been identified, including the recognition of specific docking sites, termed a D-domain and FXFP motif, on proteins that bind mitogen-activated protein kinases (MAPKs). We recently found that phosphatidylinositol-specific phospholipase C-γ1 (PLC-γ1) directly binds to extracellular signal-regulated kinase 2 (ERK2), a MAPK, via a D-domain-dependent mechanism. In addition, we identified D-domain sequences in several other PLC isozymes. In the present studies we sought to determine whether MAPK docking sequences could be recognized in other enzymes that metabolize phosphatidylinositols (PIs), as well as in enzymes that metabolize inositol phosphates (IPs).

Respiratory failure secondary to rib fractures is a major source of morbidity and mortality in trauma patients, particularly in older populations. Management of pain in these patients is complex due to the nature of the injuries. We present 3 patients who underwent a video-assisted thoracoscopic cryoablation of intercostal nerves for pain control after chest trauma. None of the patients developed post-operative complications related to poor respiratory status such as pneumonia or atelectasis. At one-month clinic follow-up, all patients reported no chest pain and were not using opiate analgesics. In patients for whom there is a contraindication to rib fixation in the setting of unstable rib fractures, cryoablation may be a method by which to improve respiratory status and decrease ventilator dependency due to pain. Cryoablation of intercostal nerves may provide a more durable and clinically feasible solution to aid in the healing process of these patients.