  The knowledge of the physical conditions occurring in the relativistic jet of
radio-loud active galactic nuclei (AGNs) is important to understand the
mechanisms at the basis of their multiband emission. From parsec-scale radio
observations of blazar objects it has been suggested a connection between the
ejection of new jet features and strong gamma-ray flares. We present results
from multi-epoch Very Long Baseline Interferometer (VLBI) and Space-VLBI
observations of the Flat Spectrum Radio Quasar (FSRQ) PKS 1510-089. The
comparison of the radio structure observed at different epochs shows the
presence of jet features moving with highly superluminal apparent velocity.
Radio flux density variability and changes in the source structure and in the
polarization properties are then compared with the information on the gamma-ray
emission in order to find a possible connection between radio and gamma-ray
emission.
