INTRODUCTION: The role of extracellular matrix and its cellular receptors in acquisition of proper dendrite morphology in neurons has remained enigmatic. Previously we have shown that CD44 adhesion molecule, the main hyaluronan receptor, plays a crucial inhibitory role in dendritic tree arborization. Additionally, our results clearly demonstrate that CD44 defines the structure of Golgi apparatus, suggesting that CD44 may regulate dendritic arbor development by modulating the Golgi apparatus morphology and positioning AIM(S): The aim of our work is to find molecular partners of CD44 in neurons. METHOD(S): Immunoprecipitation and subsequent mass spectrometry analysis were used to unravel new CD44-interacting proteins in cortical neurons cultured in vitro. Obtained results were validated by Western Blot analysis. RESULTS: Mass spectrometry analysis pointed out several potential CD44-interacting partners in neurons. In the group of identified proteins we have distinguished many molecules involved in cellular vesicles transport. One of them is ERC2, the protein that belongs to Rab3-interacting molecule (RIM)‑binding protein family. We confirmed the results obtained by mass spectrometry by immunoprecipitation and Western Blot methods. ERC2 protein was co-immunoprecipitated with anti-CD44 antibody, but not with the IgG control antibody. CONCLUSIONS: We have shown for the first time, that CD44 interacts with ERC2 in neurons. These results suggest that the cellular mechanism underlying CD44-dependent modulation of dendritic tree development involves the regulation of cellular vesicular transport in neuronal cells. FINANCIAL SUPPORT: 2014/15/N/NZ4/01912.