The big and intricate dreams of little organelles: Embracing complexity in the study of membrane traffic

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138421/1/tra12497_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138421/2/tra12497-sup-0001-EditorialProcess.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138421/3/tra12497.pd

Critical role for scaffolding adapter Gab2 in FcγR-mediated phagocytosis

Grb2-associated binder 2 (Gab2), a member of the Dos/Gab subfamily scaffolding molecules, plays important roles in regulating the growth, differentiation, and function of many hematopoietic cell types. In this paper, we reveal a novel function of Gab2 in Fcγ receptor (FcγR)–initiated phagocytosis in macrophages. Upon FcγR activation, Gab2 becomes tyrosyl phosphorylated and associated with p85, the regulatory subunit of phosphoinositide 3-kinase (PI3K), and the protein–tyrosine phosphatidylinositol Shp-2. FcγR-mediated phagocytosis is severely impaired in bone marrow–derived macrophages from Gab2−/− mice. The defect in phagocytosis correlates with decreased FcγR-evoked activation of Akt, a downstream target of PI3K. Using confocal fluorescence microscopy, we find that Gab2 is recruited to the nascent phagosome, where de novo PI3K lipid production occurs. Gab2 recruitment requires the pleckstrin homology domain of Gab2 and is sensitive to treatment with the PI3K inhibitor wortmannin. The Grb2 binding site on Gab2 also plays an auxiliary role in recruitment to the phagosome. Because PI3K activity is required for FcγR-mediated phagocytosis, our results indicate that Gab2 acts as a key component of FcγR-mediated phagocytosis, most likely by amplifying PI3K signaling in the nascent phagosome

An electrostatic switch displaces phosphatidylinositol phosphate kinases from the membrane during phagocytosis

PIP5K is held at the membrane of forming phagosomes by a conserved, positively charged patch. During particle engulfment, the surface charge of the phagosome decreases, releasing PIP5K and enabling phagocytosis to proceed

Distinct roles of class I and class III phosphatidylinositol 3-kinases in phagosome formation and maturation

Phagosomes acquire their microbicidal properties by fusion with lysosomes. Products of phosphatidylinositol 3-kinase (PI 3-kinase) are required for phagosome formation, but their role in maturation is unknown. Using chimeric fluorescent proteins encoding tandem FYVE domains, we found that phosphatidylinositol 3-phosphate (PI[3]P) accumulates greatly but transiently on the phagosomal membrane. Unlike the 3′-phosphoinositides generated by class I PI 3-kinases which are evident in the nascent phagosomal cup, PI(3)P is only detectable after the phagosome has sealed. The class III PI 3-kinase VPS34 was found to be responsible for PI(3)P synthesis and essential for phagolysosome formation. In contrast, selective ablation of class I PI 3-kinase revealed that optimal phagocytosis, but not maturation, requires this type of enzyme. These results highlight the differential functional role of the two families of kinases, and raise the possibility that PI(3)P production by VPS34 may be targeted during the maturation arrest induced by some intracellular parasites

POTÊNCIA AERÓBIA DE PRATICANTES DE HANDEBOL EM CADEIRA DE RODAS ATRAVÉS DE UM TESTE DE QUADRA

This study aimed to evaluate the aerobic power of Wheelchair Handball players through a method of field test (12 minutes). The sample of this study was of nine persons (n=9), affected by several physical disabilities, such as the sequel of poliomyelitis (n=4), spinal cord injury (n=3), lower limb amputation (n=1) and syndrome Charcot-Marie Tooth disease (n=1). The test consisted to go through a 12 minutes route of 25 x 15 meters, using the specific wheelchair for doing sports, and each athlete used his own chair. By distance, we calculated the estimated value of VO2max, according to the protocol of Franklin et al. (1990). The statistical analysis was made using SPSS 9.0 with value of p<0.05. The medium value of VO2max found was 22.79 (± 5.12) ml.kg.min-1, with minimum value of 12.2 and maximum of 29.47 ml.kg.min-1. In relation to heart rate, were found significant differences between the moments of rest, final and recovery of the test. These results, according to the classification of Franklin et al. (1990), show an average level of conditioning for this group studied. Esse estudo teve por objetivo avaliar a potência aeróbia de praticantes de Handebol em Cadeira de Rodas, através de um método de quadra (teste de 12 minutos). A amostra desse estudo foi de nove sujeitos (n=9), acometidos por diversas deficiências, tais quais sequela de poliomielite (n=4), lesão medular (n=3), amputação de membro inferior (n=1) e síndrome de Charcot-Marie Tooth (n=1). O teste consistiu em percorrer 12 minutos o percurso de 25 x 15 metros utilizando-se da cadeira de rodas específica para a prática esportiva e, cada atleta fez uso de sua cadeira. Através da distância percorrida, foi calculado o valor estimado do VO2máx, conforme protocolo de Franklin et al. (1990). A análise estatística foi realizada através do SPSS 9.0 com valor de p<0,05. O valor médio de VO2máx encontrado foi 22,79 (±5,12) ml.kg.min-1, com valores mínimo de 12,2 e máximo 29,47 ml.kg.min-1. Em relação à frequência cardíaca foram encontradas diferenças significativas entre os momentos de repouso, final e de recuperação do teste. Esses resultados, de acordo com a classificação de Franklin et al. (1990), demonstram um nível médio de condicionamento para o grupo estudado