BACKGROUND: Colony-stimulating factor-1 (CSF-1), a growth and survival factor for osteoclasts, stimulates these cells to spread and migrate towards a gradient of CSF-1. This may support the translocation of osteoclasts to new sites on the bone surface to be resorbed. Phosphoinositide 3-kinase (PI 3-K) is a lipid kinase participating in various signal transduction pathways. OBJECTIVE: To investigate the role of PI 3-K in the CSF-1-induced spreading of osteoclasts. METHODS: In isolated rat osteoclasts treated with or without CSF-1, the distribution of PI 3-K and proteins phosphorylated on tyrosine were investigated using immunofluorescence. In murine osteoclast-like cells grown from bone marrow cells co-cultured with osteoblasts, the activation of the PI 3-K by CSF-1 was determined both in vivo and in vitro. In vivo, the enzyme product in the cell was determined after extraction and separation with thin layer chromatography; in vitro, PI 3-K activity was measured in the pellet immunoprecipitated from the cell lysate. RESULTS: Inhibition of PI 3-K blocked the CSF-1-induced spreading of osteoclasts. In spreading osteoclasts, a portion of PI 3-K was translocated to the periphery where proteins phosphorylated on tyrosine appeared simultaneously. In osteoclast-like cells, CSF-1 stimulated PI 3-K activity. This activity could be immunoprecipitated with antibody against phophotyrosine residues. CONCLUSION: PI 3-K participates in the CSF-1-induced spreading of osteoclasts. The activated PI 3-K may induce the reorganization of the cytoskeleton resulting in spreading and migration.
S. Kofman-Alfaro, E. Valdés, J. Terá, S. S. Wachtel, B. Chávez, S. Bassol, M. Medina and G. Pérez-Palacios
Abstract. To clarify the origin of the genital ambiguity occasionally associated with the XX male syndrome, a series of endocrinological studies were undertaken in an affected 6 months old infant with perineoscrotal hypospadias. The patient fulfilled all the diagnostic criteria of the syndrome: the testes were descended bilaterally, the Mullerian derivatives were absent, the 46,XX chromosome complement was ascertained in different cell lines, and male levels of H-Y antigen were detected in cultured skin fibroblasts. Circulating gonadotrophin levels and pituitary LRH responsiveness were within normal limits for the age group. Serum testosterone (T) levels were normal, and gonadal stimulation with hCG caused a significant rise on serum T. Incubations of [3H]T with fibroblasts from genital skin revealed normal activity of steroid 5α-reductase. Moreover, normal concentrations of thermostable cytosol androgen receptors were revealed in cultured fibroblasts. Altogether the results indicated that ambiguity of the external genitalia in this patient was the result of neither abnormal T biosynthesis, peripheral A-ring T reduction, nor androgen intracellular specific binding, and suggested that the nature of the imcomplete virilization could be a non-endocrine independent event associated to this disorder. The data are also consistent with the notion that testicular impairment observed in adult XX males develops later in life.