Lysines residing in putative Small Ubiquitin-like MOdifier (SUMO) motifs regulate fate and function of 37 KDa laminin receptor.

There is a putative precursor to mature receptor relationship between 37 Laminin Receptor (LR) and 67 LR. As such, the pair are frequently referred to as a single entity, the 37/67 kDa Laminin Receptor (37/67 LR) and 67 LR was identified as a laminin binding entity. 37/67 LR has been of clinical interest for many years, as 37/67 LR is a prognostic indicator for many cancers including breast, lung, colon, and prostate. However, the genesis of 67 LR is controversial, and confounded by its stability under SDS-PAGE conditions, a lack of splice variants, and the existence of post-translational modifications that cannot account for the mass discrepancy between 37 and 67 LR. In the present work, we mutated potential SUMO motif sites (Lysine residues) in 37 LR and generated a series of 37 LR-expressing plasmids with a C-terminal histidine tag. We report an inability to detect 67 LR formation, suggesting that SUMOylation does not appear to directly occur at the lysine residues proposed. However, the work revealed that these lysine mutations still appear to be important and can impact the fate and function of 37 LR, by impairing half-life and steady state pre-mRNA levels. These results suggest that the Lys residues within putative SUMO motifs of 37 LR are important for 37 LR function.