Alexander Meves

The Kindlin protein family: new members to the club of focal adhesion proteins

Kindlins are a group of proteins that have recently attracted attention for their ability to bind and activate integrins. Moreover, they have also been linked to inherited and acquired human diseases including Kindler syndrome, leukocyte adhesion deficiency, and cancer. Although most studies have focused on kindlins as key regulatory components of cell-extracellular matrix junctions such as focal adhesions, preliminary data suggest the involvement of additional cellular compartments in mediating their functions, particularly at cell-cell contacts and the nucleus. Investigating the many roles of kindlins is likely to expand and sharpen our view on the versatility of integrin-mediated cell adhesion, the nuclear function of focal adhesion proteins, and the crosstalk between cell-cell and cell-matrix adhesions in health and disease.

H2O2 is required for UVB-induced EGF receptor and downstream signaling pathway activation

Ultraviolet radiation (UVR)-induced receptor phosphorylation is increasingly recognized as a widely occurring phenomenon. However, the mechanisms, mediators, and sequence of events involved in this process remain ill-defined. We have recently shown that exposure of human keratinocytes to physiologic doses of ultraviolet B radiation (UVB) activates epidermal growth factor receptor (EGFR)/extracellular-regulated kinase 1 and 2 (ERK1/2), and p38 signaling pathways via reactive oxygen species. Here we demonstrate that UVB exposure increased intra- and extracellular H2O2 production rapidly in a time-dependent manner. An EGFR-specific monoclonal antibody abrogated EGFR autophosphorylation and markedly decreased the phosphorylation of ERK1/2 whereas p38 activation was unaffected. Overexpression of catalase strongly inhibited UVB-induced EGFR/ERK1/2 pathway activation. These findings establish the sequence of events after UVB irradiation: (i) H2O2 generation, (ii) EGFR phosphorylation, and (iii) ERK activation. Our results identify UVB-induced H2O2 as a second messenger that is required for EGFR and dependent downstream signaling pathways activation.

UVB-induced Epidermal Growth Factor Receptor Phosphorylation is Critical for Downstream Signaling and Keratinocyte Survival¶

Abstract We have recently shown that UVB radiation activates epidermal growth factor receptor (EGFR)/extracellular regulated kinase 1 and 2 (ERK1/2) and p38 signaling pathways in keratinocytes. However, the functional relevance of these processes for downstream signaling and cell survival remains to be determined. The specific EGFR inhibitor PD153035 markedly decreased UVB-induced phosphorylation of EGFR, ERK1/2 and shc, whereas p38 activation was unaffected. PD153035 pretreatment followed by UVB reduced clonogenic potential and enhanced peroxide production, apoptosis and cell death. Our data suggest that ligand-independent phosphorylation of EGFR and likely dependent downstream signaling pathways regulate cellular defense mechanisms important for cell survival following oxidative stress.

Cocaine abuse : Dermatologic manifestations and therapeutic approaches

Cocaine affects the cutaneous system and other organ systems. Cocaine use is associated with vasculitides, infectious complications, and numerous dermatologic conditions. It has been associated with formication (ie, tactile hallucinations of insects crawling underneath the skin), which leads to delusions of parasitosis and other psychosis-related dermatologic disorders. When a patient presents to a dermatology clinic with chronic skin lesions, a vague medical history, negative findings from previous evaluations, labile affect, and delusional behavior, drug screening should be performed to identify possible cocaine use.

H2O2 mediates oxidative stress-induced epidermal growth factor receptor phosphorylation

We used a well-established thiol-alkylating agent, N-ethylmaleimide (NEM), to oxidatively stress human keratinocytes. Time course studies revealed that NEM rapidly depleted keratinocytes of reduced glutathione (GSH), which was followed by rapidly increasing levels of intracellular reactive oxygen species (ROS) and subsequently by phosphorylation of epidermal growth factor receptor (EGFR). Pretreatment with antioxidants or enhanced catalase activity in keratinocytes inhibited ROS/H(2)O(2) accumulation and EGFR phosphorylation, demonstrating that H(2)O(2) production is a mediator required for EGFR phosphorylation. Collectively, these results suggest a sequence of events leading to EGFR phosphorylation which is likely shared by oxidative stress-inducing agents, namely: (1) GSH depletion; (2) H(2)O(2) accumulation; and (3) EGFR phosphorylation. We propose that depletion of GSH and accumulation of H(2)O(2) are upstream events and critical mediators required for ligand-independent phosphorylation of growth factor receptors in response to oxidative stress.

Tumor Cell Adhesion As a Risk Factor for Sentinel Lymph Node Metastasis in Primary Cutaneous Melanoma

PURPOSE Less than 20% of patients with melanoma who undergo sentinel lymph node (SLN) biopsy based on American Society of Clinical Oncology/Society of Surgical Oncology recommendations are SLN positive. We present a multi-institutional study to discover new molecular risk factors associated with SLN positivity in thin and intermediate-thickness melanoma. PATIENTS AND METHODS Gene clusters with functional roles in melanoma metastasis were discovered by next-generation sequencing and validated by quantitative polymerase chain reaction using a discovery set of 73 benign nevi, 76 primary cutaneous melanoma, and 11 in-transit melanoma metastases. We then used polymerase chain reaction to quantify gene expression in a model development cohort of 360 consecutive thin and intermediate-thickness melanomas and a validation cohort of 146 melanomas. Outcome of interest was SLN biopsy metastasis within 90 days of melanoma diagnosis. Logic and logistic regression analyses were used to develop a model for the likelihood of SLN metastasis from molecular, clinical, and histologic variables. RESULTS ITGB3, LAMB1, PLAT, and TP53 expression were associated with SLN metastasis. The predictive ability of a model that included these molecular variables in combination with clinicopathologic variables (patient age, Breslow depth, and tumor ulceration) was significantly greater than a model that only considered clinicopathologic variables and also performed well in the validation cohort (area under the curve, 0.93; 95% CI, 0.87 to 0.97; false-positive and false-negative rates of 22% and 0%, respectively, using a 10% cutoff for predicted SLN metastasis risk). CONCLUSION The addition of cell adhesion-linked gene expression variables to clinicopathologic variables improves the identification of patients with SLN metastases within 90 days of melanoma diagnosis.

Vitamin E analog modulates UVB-induced signaling pathway activation and enhances cell survival

We have recently shown that exposure of human keratinocytes to physiologic doses of ultraviolet B (UVB) activates epidermal growth factor receptor (EGFR)/extracellular-regulated kinases 1 and 2 (ERK1/2) and p38 signaling pathways via reactive oxygen species, an effect that can be modulated by antioxidants. Trolox, a water-soluble vitamin E analog, is among the antioxidants that are currently being investigated for their preventive and protective potential against harmful effects of UV radiation to the skin. We found that Trolox inhibits both basal and UVB-induced intracellular H(2)O(2) generation in primary keratinocytes in a concentration-dependent manner. Trolox did not significantly affect UVB-induced phosphorylation of EGFR. Stronger inhibition was observed for ERK1/2 activation at lower, and for p38 activation at higher, concentrations of Trolox added to cells before exposure to UVB. Similarly different effects were found with regard to length of pretreatment with Trolox before UVB exposure-increasing inhibition for ERK1/2 activation at shorter, and for p38 activation at longer, pretreatment intervals. UVB-induced c-jun-N-terminal kinase activation was potently suppressed by Trolox. Also, increasing the pretreatment time of Trolox decreased the rate of cell death following UVB. In conclusion, UVB-induced signaling pathway activation is differentially modulated by Trolox. Further investigation into the time-dependent biologic activation of Trolox and its metabolic products, and modulation of signal transduction with cell outcome should facilitate development of rational strategies for pharmacologic applications.

A survey of case reports and case series of therapeutic interventions in the Archives of Dermatology.

Background  Case reports and case series are often the first line of clinical evidence in the medical literature and, until stronger evidence becomes available, are the only guidance to new therapies.

Antipsoriatic drug anthralin induces EGF receptor phosphorylation in keratinocytes: requirement for H2O2 generation

Abstract: Even though anthralin is a well‐established topical therapeutic agent for psoriasis, little is known about its effects and biochemical mechanisms of signal transduction. In contrast to a previous report, we found that anthralin induced time‐ and concentration‐dependent phosphorylation of epidermal growth factor receptor in primary human keratinocytes. Four lines of evidence show that this process is mediated by reactive oxygen species. First, we found that anthralin induces time‐dependent generation of H2O2. Second, there is a correlation between a time‐dependent increase in anthralin‐induced epidermal growth factor receptor phosphorylation and H2O2 generation. Third, the structurally different antioxidants n‐propyl gallate and N‐acetylcysteine inhibited epidermal growth factor receptor phosphorylation induced by anthralin. Fourth, overexpression of catalase inhibited this process. The epidermal growth factor receptor‐specific tyrosine kinase inhibitor PD153035 abrogated anthralin‐induced epidermal growth factor receptor phosphorylation and activation of extracellular‐regulated kinase 1/2. These findings establish the following sequence of events: (1) H2O2 generation, (2) epidermal growth factor receptor phosphorylation, and (3) extracellular‐regulated kinase activation. Our data identify anthralin‐induced reactive oxygen species and, more specifically, H2O2 as an important upstream mediator required for ligand‐independent epidermal growth factor receptor phosphorylation and downstream signaling.

Sorting Nexin 31 Binds Multiple β Integrin Cytoplasmic Domains and Regulates β1 Integrin Surface Levels and Stability

Trafficking of α5β1 integrin to lysosomes and its subsequent degradation is influenced by ligand occupancy and the binding of SNX17 via its protein 4.1, ezrin, radixin, moesin (FERM) domain to the membrane-distal NPxY motif in the cytoplasmic domain of β1 integrin in early endosomes. Two other sorting nexin (SNX) family members, namely SNX27 and SNX31, share with SNX17 next to their obligate phox domain a FERM domain, which may enable them to bind β integrin tails. Here we report that, in addition to SNX17, SNX31 but not SNX27 binds several β integrin tails in early endosomes in a PI3 (phosphatidylinositide 3)-kinase-dependent manner. Similarly like SNX17, binding of SNX31 with β1 integrin tails in early endosomes occurs between the FERM domain and the membrane-distal NPxY motif in the β1 integrin cytoplasmic domain. Furthermore, expression of SNX31 rescues β1 integrin surface levels and stability in SNX17-depleted cells. In contrast to SNX17, expression of SNX31 is restricted and found highly expressed in bladder and melanoma tissue. Altogether, these results demonstrate that SNX31 is an endosomal regulator of β integrins with a restricted expression pattern.