Investigation of the components of the 67-kDa laminin receptor-dependent protein phosphatase 2A activating signalling pathway

Abstract

The 67 kDa laminin receptor (67LR) is a non-integrin cell surface receptor derived from the 37 kDa precursor (37LRP) and is involved in cell adhesion. It also acts as a high-affinity receptor for epigallocatechin-3-gallate (EGCG), which can suppress tumor growth and induce apoptosis via various signaling pathways. One such pathway, involving the EGCG/67LR/cAMP/PKA/PP2A/MP cascade, activates tumor suppressor proteins through the dephosphorylation by protein phosphatase 2A (PP2A) and myosin phosphatase (MP). This study aims to elucidate the EGCG-67LR interaction and the role of B56 isoforms in MP activation. Using HEK293AD cells, the presence of the receptor in the plasma membrane was confirmed, making them suitable for interaction studies. An inducible CRISPR/Cas9 system in HeLa cells was employed to eliminate B56δ, revealing that its downregulation leads to increased phosphorylation of MYPT1, indicating that B56δ targets PP2A to MP.