Ocular Albinism: evidence for a defect in an intracellular signal transduction system.

G protein-coupled receptors (GPCRs) participate in the most common signal transduction system at the plasma membrane. The wide distribution of heterotrimeric G proteins in the internal membranes suggests that a similar signalling mechanism might also be used at intracellular locations. We provide here structural evidence that the protein product of the ocular albinism type 1 gene (OA1), a pigment cell-specific integral membrane glycoprotein, represents a novel member of the GPCR superfamily and demonstrate that it binds heterotrimeric G proteins. Moreover, we show that OA1 is not found at the plasma membrane, being instead targeted to specialized intracellular organelles, the melanosomes. Our data suggest that OA1 represents the first example of an exclusively intracellular GPCR and support the hypothesis that GPCR-mediated signal transduction systems also operate at the internal membranes in mammalian cells

As desigualdades escolares antes e depois da escola: organização escolar e influência dos diplomas

School reproduces social inequalities everywhere as it is more favorable to already advantaged pupils. This is, however, a too general "law" for explaining the large variations revealed by international comparisons in the amplitude of this reproduction. Relying upon these studies, this paper shows first that these variations cannot be explained directly by the amplitude of social inequalities. In order to explain them, two other factors must be raised. The first one concerns the organization of the school systems, which may either widen or mitigate the impact of pupils' social background on their academic achievement. The second one concerns the influence of diplomas on access to various social positions. The paper shows that the more diplomas play a deciding role, the more pronounced are school inequalities and the more acute is the reproduction of social inequalities. Finally, it is not only what is produced in school and through its operation that determines the amplitude of the reproduction, but the own role attributed to school by the various societies. This study achieved on a sample of countries stands at an aggregate level, and some qualitative complementary studies would be very useful for better understand how social reproduction operates.A escola reproduz as desigualdades sociais por ser mais favorável aos alunos social e culturalmente privilegiados. No entanto, essa "lei" é demasiado geral para explicar as grandes variações na amplitude dessa reprodução, reveladas pelas comparações internacionais. Partindo desses estudos, o artigo mostra, em primeiro lugar, que essas variações não se explicam diretamente pela amplitude das desigualdades sociais. Para explicá-las é preciso levantar duas outras questões. A primeira tange à organização dos sistemas escolares, os quais podem aumentar ou atenuar o impacto das desigualdades sociais sobre as desigualdades escolares. A segunda se refere aos impactos da escola, à influência dos diplomas para a mobilidade social. O artigo demonstra que, quanto mais determinante for o papel dos diplomas, mais marcadas serão as desigualdades escolares e mais rígida será a reprodução das desigualdades sociais. Finalmente, a função atribuída à escola pelas diversas sociedades determinará a amplitude da reprodução social. Contudo, essa análise foi realizada a partir de uma amostra de países, logo a realização de estudos qualitativos complementares seria muito útil para melhor compreender como ocorre a reprodução social