Integrin alpha 2 beta 1 promotes activation of protein phosphatase 2A and dephosphorylation of Akt and glycogen synthase kinase 3 beta

Serine/threonine kinase Akt is a downstream effector protein of phosphatidylinositol-3-kinase (PI-3K). Many integrins can function as positive modulators of the PI-3K/Akt pathway. Integrin alpha 2 beta 1 is a collagen receptor that has been shown to induce specific signals distinct from those activated by other integrins. Here, we found that, in contrast what was found for cells adherent to fibronectin, alpha 2 beta 1-mediated cell adhesion to collagen leads to dephosphorylation of Akt and glycogen synthase kinase 3 beta (GSK3 beta) and concomitantly to the induction of protein serine/threonine phosphatase 2A (PP2A) activity. PP2A activation can be inhibited by mutation in the alpha 2 cytoplasmic domain and by a function-blocking anti-alpha 2 antibody. Akt can be coprecipitated with PP2A, and coexpression of Akt with PP2Ac (catalytic subunit) inhibits Akt kinase activity. Integrin alpha 2 beta 1-related activation of PP2A is dependent on Cdc42. These results indicate that cell adhesion to collagen modulates Akt activity via the alpha 2 beta 1-induced activation of PP2A.     

Enhancement of fibroblast collagenase-1 (MMP-1) gene expression by tumor promoter okadaic acid is mediated by stress-activated protein kinases jun N-terminal kinase and p38

Collagenase-1 (matrix metalloproteinase-1, MMP-1) is expressed by several types of cells, including fibroblasts, and apparently plays an important role in the remodeling of collagenous extracellular matrix in various physiologic and pathologic situations. Here, we have examined the molecular mechanisms of the activation of fibroblast MMP-1 gene expression by a naturally occurring non-phorbol ester type tumor promoter okadaic acid (OA), a potent inhibitor of serine/threonine protein phosphatase 2A. We show that in fibroblasts OA activates three distinct subgroups of mitogen activated protein kinases (MAPKs): extracellular signal-regulated kinase 1,2 (ERK 1,2), c-Jun N-terminal-kinase/stress-activated protein kinase (JNK/SAPK) and p38. Activation of MMP-1 promoter by OA is entirely blocked by overexpression of dual-specificity MAPK phosphatase CL100. In addition, expression of kinase-deficient forms of ERK 1,2, SAPKβ, p38, or JNK/SAPK kinase SEK1 strongly inhibited OA-elicited activation of MMP-1 promoter. OA-elicited enhancement of MMP-1 mRNA abundance was also strongly prevented by two chemical MAPK inhibitors: PD 98059, a specific inhibitor of the activation of ERK1,2 kinases MEK1,2; and SB 203580, a selective inhibitor of p38 activity. Results of this study show that MMP-1 gene expression in fibroblasts is coordinately regulated by ERK1,2, JNK/SAPK, and p38 MAPKs and suggest an important role for the stress-activated MAPKs JNK/SAPK and p38 in the activation of MMP-1 gene expression. Based on these observations, it is conceivable that specific inhibition of stress-activated MAPK pathways may serve as a novel therapeutic target for inhibiting degradation of collagenous extracellular matrix.     

Geographic Cline in the Shape of the Moose Mandible: Indications of an Adaptive Trend

Intra-specific geographic variation is probably one of the most common patterns studied in ungulate morphology. However, the shape of the mandible, a crucial feature with regard to feeding, has been greatly understudied in this context. Here, we utilized a museum collection of moose (Alces alces) mandibles to investigate whether we could detect significant variation in this species, and test for the existence of geographic patterns and associations with population genetic structure. We applied a landmark-based geometric morphometrics approach, analyzing shape data with principal component analysis and linear mixed models. A significant geographic shift in the shape of the moose mandible was revealed. The main pattern was similar in both sexes; however, there was a consistent difference in shape between males and females over the latitudinal scale. The main changes included an enlargement in the attachment surfaces of the muscles controlling biting and mastication, suggesting more effective mastication towards the north, plausibly as an adaptive response to a harder and tougher wintertime diet. Additionally, more subtle, yet statistically significant age-related shape variation was discovered. Interestingly, no or only a weak association between the morphometric variation and the genetic population structure was detected with neutral molecular markers.     

High lactose tolerance in North Europeans: a result of migration, not in situ milk consumption

The main carbohydrate in milk is lactose, which must be hydrolyzed to glucose and galactose before the sugars can be digested. While 65% or more of the total human population are lactose intolerant, in some human populations lactase activity commonly persists into adulthood. Lactose tolerance is exceptionally widespread in Northern European countries such as Sweden and Finland, with tolerance levels of 74% and 82%, respectively. Theoretically, this may result either from a strong local selection pressure for lactose tolerance, or from immigration of lactose tolerant people to Northern Europe. We provide several lines of archaeological and historical evidence suggesting that the high lactose tolerance in North Europeans cannot be explained by selection from in situ milk consumption. First, fresh cow milk has not belonged to the traditional diet of Swedes or Finns until recent times. Second, not enough milk has been available for adult consumption. Cattle herding has been neither widespread nor productive enough in Northern Europe to have provided constant access to fresh milk. We suggest that the high prevalence of lactose tolerance in Finland in particular may be explained by immigration of people representing so-called Corded Ware Culture, an early culture representing agricultural development in Europe.     

CCHCR1 Is Up-Regulated in Skin Cancer and Associated with EGFR Expression

Despite chronic inflammation, psoriatic lesions hardly ever progress to skin cancer. Aberrant function of the CCHCR1 gene (Coiled-Coil α-Helical Rod protein 1, HCR) within the PSORS1 locus may contribute to the onset of psoriasis. As CCHCR1 is expressed in certain cancers and regulates keratinocyte (KC) proliferation in a transgenic mouse model, we studied its relation to proliferation in cutaneous squamous cell cancer (SCC) cell lines by expression arrays and quantitative RT-PCR and in skin tumors by immunohistochemistry. CCHCR1 protein was detected in the pushing border of SCC and lining basal cell carcinoma islands. Different from psoriasis, Ki67 had a similar expression pattern as CCHCR1. The most intense CCHCR1 staining occurred in areas positive for epidermal growth factor receptor (EGFR). Expression of CCHCR1 mRNA was upregulated 30–80% in SCC lines when compared to normal KCs and correlated positively with Ki67 expression. The most aggressive and invasive tumor cell lines (RT3, FaDu) expressed CCHCR1 mRNA less than non-tumorigenic HaCaT cells. Moreover, the tumor promoters okadaic acid and menadione downregulated CCHCR1 mRNA. We conclude that both in psoriasis and the early stages of KC transformation, CCHCR1 may function as a negative regulator of proliferation, but beyond a certain point in oncogenesis cannot control this phenomenon any longer.     

Europium as a label in time-resolved immunofluorometric assays

A nonisotopic immunoassay has been developed based on a sensitive detection of europium (III) in water solution using time-resolved fluorometry. The europium label is bound to the antibody with EDTA derivatives, either diazophenyl-EDTA-Eu or isothiocyanatophenyl-EDTA-Eu. After the immunometric assay has been completed the europium is preferably dissociated from the antibody at low pH and measured by time-resolved fluorescence in a micellar solution containing Triton X-100, β-diketone, and a Lewis base. The detergent solubilizes the chelating compounds in the solution and excludes water from the fluorescent ligand-europium complex. Europium concentrations as low as 5·10^?14m were measured using a 1-s counting time. The sensitivity of the immunoassay of rabbit IgG used as a model system was 25 pg/ml (6 pg/assay).