  Narrow-line Seyfert 1 galaxies (NLS1) are an intriguing subclass of active
galactic nuclei. Their observed properties indicate low central black hole mass
and high accretion rate. The extremely radio-loud NLS1 sources often show
relativistic beaming and are usually regarded as younger counterparts of
blazars. Recently, the object SDSS J110006.07+442144.3 was reported as a
candidate NLS1 source. The characteristics of its dramatic optical flare
indicated its jet-related origin. The spectral energy distribution of the
object was similar to that of the gamma-ray detected radio-loud NLS1, PMN
J0948+0022. Our high-resolution European Very Long Baseline Interferometry
Network observations at 1.7 and 5 GHz revealed a compact core feature with a
brightness temperature of >~ 10^(10) K. Using the lowest brightness temperature
value and assuming a moderate Lorentz factor of ~9 the jet viewing angle is <~
26 deg. Archival Very Large Array data show a large-scale radio structure with
a projected linear size of ~150 kpc reminiscent of double-sided morphology.
