Dynamics of the α6β4 Integrin in Keratinocytes

The integrin α6β4 has been implicated in two apparently contrasting processes, i.e., the formation of stable adhesions, and cell migration and invasion. To study the dynamic properties of α6β4 in live cells two different β4-chimeras were stably expressed in β4-deficient PA-JEB keratinocytes. One chimera consisted of full-length β4 fused to EGFP at its carboxy terminus (β4-EGFP). In a second chimera the extracellular part of β4 was replaced by EGFP (EGFP-β4), thereby rendering it incapable of associating with α6 and thus of binding to laminin-5. Both chimeras induce the formation of hemidesmosome-like structures, which contain plectin and often also BP180 and BP230. During cell migration and division, the β4-EGFP and EGFP-β4 hemidesmosomes disappear, and a proportion of the β4-EGFP, but not of the EGFP-β4 molecules, become part of retraction fibers, which are occasionally ripped from the cell membrane, thereby leaving “footprints” of the migrating cell. PA-JEB cells expressing β4-EGFP migrate considerably more slowly than those that express EGFP-β4. Studies with a β4-EGFP mutant that is unable to interact with plectin and thus with the cytoskeleton (β4(R1281W)-EGFP) suggest that the stabilization of the interaction between α6β4 and LN-5, rather than the increased adhesion to LN-5, is responsible for the inhibition of migration. Consistent with this, photobleaching and recovery experiments revealed that the interaction of β4 with plectin renders the bond between α6β4 and laminin-5 more stable, i.e., β4-EGFP is less dynamic than β4(R1281W)-EGFP. On the other hand, when α6β4 is bound to laminin-5, the binding dynamics of β4 to plectin are increased, i.e., β4-EGFP is more dynamic than EGFP-β4. We suggest that the stability of the interaction between α6β4 and laminin-5 is influenced by the clustering of α6β4 through the deposition of laminin-5 underneath the cells. This clustering ultimately determines whether α6β4 will inhibit cell migration or not

Rendimento corporal e composição química de jundiás alimentados com diferentes níveis de proteína e energia na dieta, criados em tanques-rede Catfish (jundia) body yield and chemical composition fed different protein and energy level in the diet, reared in net-tanks

Objetivou-se analisar o rendimento corporal e a composição química de jundiás, Rhamdia quelen, alimentados com rações contendo diferentes níveis de proteína e energia e criados em sistema de tanques-rede. Utilizou-se a densidade inicial de 70 peixes/m³, em 18 tanques-rede (5,0 m³), durante 324 dias. O delineamento experimental foi inteiramente casualizado com dois fatores - níveis de proteína bruta (PB), 25, 30 ou 35%; e níveis de energia digestível (ED): 3.250 e 3.500 kcal - e três repetições. A dieta foi fornecida à vontade, mas mensurada diariamente. No início, um lote de peixes foi sacrificado para determinação dos parâmetros corporais e químicos. A cada 28 dias, dois peixes de cada unidade experimental foram abatidos para determinação dos comprimentos total e padrão, do peso total e dos pesos de fígado, gônadas, cabeça, tronco limpo e gordura visceral, respectivamente. Posteriormente, foram realizados cálculos dos índices hepatossomático e gonadossomático, da porcentagem de cabeça e do rendimento de carcaça e do rendimento de tronco limpo. A partir do mês de junho de 2006, também foram registrados o rendimento de filé e o sexo dos indivíduos. Para determinação da composição da carne do jundiá, foram realizadas as análises químicas de umidade, proteína bruta, lipídios e matéria mineral. O fornecimento da ração com 30% de PB resultou em maior rendimento de tronco limpo. A composição do músculo não foi influenciada pelas dietas testadas. Os melhores resultados foram obtidos com a utilização de dietas contendo 30% de PB e 3.250 kcal de energia digestível/kg.<br>The objective of this study was to analyze the body yield and the chemical composition of catfish (jundia), Rhamdia quelen, reared in net-tanks and fed with diets containing different levels of protein and energy. An initial density of 70 fish/m³, in 18 net-tanks (5.0 m³) was used, for 324 days. A randomized complete design was used, with two factors: Crude Protein (CP) at three levels, 25, 30 and 35%; and Digestible energy (DE) at two levels, 3,250 and 3,500 kcal, and three replications. The diet was given freely, but it was measured daily. At the beginning of the experiment, one group of fish was killed to determine the body and chemical parameters. Every 28 days, two individuals of each experimental unit were killed and measured: total and standard length, total weight, liver, gonads, head, clean torso (CT) and visceral fat weight, respectively. Subsequently, the hepatosomatic index, gonadosomatic index, head percentage, carcass and clean torso yield were calculated. The fillet yield and the sex of the individuals were also registered from June/2006 on. Analyses of humidity, crude protein, lipids and mineral matter were conducted for the chemical composition of the jundia meat. Feed with 30% CP provided fish with better clean torso yield. The muscle composition was not influenced by the tested diets. The best result was obtained using diets containing 30% CP and 3,250 kcal digestible energy/kg