Spatial restriction of alpha4 integrin phosphorylation regulates lamellipodial stability and alpha4beta1-dependent cell migration.

Integrins coordinate spatial signaling events essential for cell polarity and directed migration. Such signals from alpha4 integrins regulate cell migration in development and in leukocyte trafficking. Here, we report that efficient alpha4-mediated migration requires spatial control of alpha4 phosphorylation by protein kinase A, and hence localized inhibition of binding of the signaling adaptor, paxillin, to the integrin. In migrating cells, phosphorylated alpha4 accumulated along the leading edge. Blocking alpha4 phosphorylation by mutagenesis or by inhibition of protein kinase A drastically reduced alpha4-dependent migration and lamellipodial stability. alpha4 phosphorylation blocks paxillin binding in vitro; we now find that paxillin and phospho-alpha4 were in distinct clusters at the leading edge of migrating cells, whereas unphosphorylated alpha4 and paxillin colocalized along the lateral edges of those cells. Furthermore, enforced paxillin association with alpha4 inhibits migration and reduced lamellipodial stability. These results show that topographically specific integrin phosphorylation can control cell migration and polarization by spatial segregation of adaptor protein binding

Spatial restriction of α4 integrin phosphorylation regulates lamellipodial stability and α4β1-dependent cell migration

Întegrins coordinate spatial signaling events essential for cell polarity and directed migration. Such signals from α4 integrins regulate cell migration in development and in leukocyte trafficking. Here, we report that efficient α4-mediated migration requires spatial control of α4 phosphorylation by protein kinase A, and hence localized inhibition of binding of the signaling adaptor, paxillin, to the integrin. In migrating cells, phosphorylated α4 accumulated along the leading edge. Blocking α4 phosphorylation by mutagenesis or by inhibition of protein kinase A drastically reduced α4-dependent migration and lamellipodial stability. α4 phosphorylation blocks paxillin binding in vitro; we now find that paxillin and phospho-α4 were in distinct clusters at the leading edge of migrating cells, whereas unphosphorylated α4 and paxillin colocalized along the lateral edges of those cells. Furthermore, enforced paxillin association with α4 inhibits migration and reduced lamellipodial stability. These results show that topographically specific integrin phosphorylation can control cell migration and polarization by spatial segregation of adaptor protein binding

Rap1 binding and a lipid-dependent helix in talin F1 domain promote integrin activation in tandem.

Rap1 GTPases bind effectors, such as RIAM, to enable talin1 to induce integrin activation. In addition, Rap1 binds directly to the talin1 F0 domain (F0); however, this interaction makes a limited contribution to integrin activation in CHO cells or platelets. Here, we show that talin1 F1 domain (F1) contains a previously undetected Rap1-binding site of similar affinity to that in F0. A structure-guided point mutant (R118E) in F1, which blocks Rap1 binding, abolishes the capacity of Rap1 to potentiate talin1-induced integrin activation. The capacity of F1 to mediate Rap1-dependent integrin activation depends on a unique loop in F1 that has a propensity to form a helix upon binding to membrane lipids. Basic membrane-facing residues of this helix are critical, as charge-reversal mutations led to dramatic suppression of talin1-dependent activation. Thus, a novel Rap1-binding site and a transient lipid-dependent helix in F1 work in tandem to enable a direct Rap1-talin1 interaction to cause integrin activation

Phase II Trial of Dasatinib for Patients with Acquired Resistance to Treatment with the Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors Erlotinib or Gefitinib

Introduction:Dual inhibition of SRC- and EGFR-dependent pathways may overcome acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) for patients with lung adenocarcinoma with EGFR mutations. The SRC inhibitor dasatinib demonstrates antitumor activity in gefitinib-resistant cells lines and xenografts. Dasatinib is tolerable for patients with advanced non-small cell lung cancer, and in combination with erlotinib.Methods:We conducted this phase II study of dasatinib 70 mg twice daily in patients with EGFR-mutant lung adenocarcinoma and acquired resistance to EGFR-TKIs. After a protocol amendment based on evolving data about both drugs, patients received dasatinib at a dose of 100 mg daily with continued erlotinib after developing acquired resistance. Enrolled patients either harbored an activating mutation in EGFR or experienced clinical benefit with single-agent erlotinib or gefitinib, followed by RECIST documented progression while being treated with an EGFR-TKI.Results:Twenty-one patients were enrolled, 9 under the original trial design and 12 after the protocol amendments. We observed no complete or partial responses (0% observed rate, 95% confidence interval: 0–18%). The median time to progression was 0.5 months (range, 0.2–1.8 months) in patients treated with dasatinib and 0.9 months (range, 0.4–5 months) for patients treated with dasatinib and erlotinib in combination. Pleural effusions and dyspnea were frequent toxicities.Conclusions:Dasatinib has no activity in patients with EGFR-mutant lung adenocarcinoma with acquired resistance to erlotinib and gefitinib

University Physics Volume 2

University Physics is a three-volume collection that meets the scope and sequence requirements for two- and three-semester calculus-based physics courses. Volume 1 covers mechanics, sound, oscillations, and waves. Volume 2 covers thermodynamics, electricity and magnetism, and Volume 3 covers optics and modern physics. This textbook emphasizes connections between theory and application, making physics concepts interesting and accessible to students while maintaining the mathematical rigor inherent in the subject. Frequent, strong examples focus on how to approach a problem, how to work with the equations, and how to check and generalize the result.https://commons.erau.edu/oer-textbook/1002/thumbnail.jp

Chronic alcohol consumption decreases brown adipose tissue mass and disrupts thermoregulation: a possible role for altered retinoid signaling

Retinoic acid, an active metabolite of dietary vitamin A, acts as a ligand for nuclear receptor transcription factors with more than 500 known target genes. It is becoming increasingly clear that alcohol has a significant impact on cellular retinoic acid metabolism, with resultant effects on its function. Here, we test the hypothesis that chronic alcohol consumption impairs retinoic acid signaling in brown adipose tissue (BAT), leading to impaired BAT function and thermoregulation. All studies were conducted in age-matched, male mice consuming alcohol-containing liquid diets. Alcohol’s effect on BAT was assessed by histology, qPCR, HPLC, LC/MS and measures of core body temperature. Our data show that chronic alcohol consumption decreases BAT mass, with a resultant effect on thermoregulation. Follow-up mechanistic studies reveal a decreased triglyceride content in BAT, as well as impaired retinoic acid homeostasis, associated with decreased BAT levels of retinoic acid in alcohol-consuming mice. Our work highlights a hitherto uncharacterized effect of alcohol on BAT function, with possible implications for thermoregulation and energy metabolism in drinkers. Our data indicate that alcohol’s effects on brown adipose tissue may be mediated through altered retinoic acid signaling