A subject-matter of the present invention is a rubber composition intended for the manufacture of tires or of tire semi-finished products, based on at least one isoprene elastomer, an inorganic filler as reinforcing filler and a polyfunctional organosiloxane coupling agent capable of providing the bonding between the reinforcing inorganic filler and the isoprene elastomer, comprising per molecule, grafted to its silicon atoms, on the one hand at least one hydroxyl or hydrolysable functional group allowing it to be grafted to the reinforcing inorganic filler and, on the other hand, at least one group bearing at least one azodicarbonyl functional group —CO—N═N—CO— allowing it to be grafted to the isoprene elastomer.