S100A6 is a positive regulator of PPP5C-FKBP51-dependent regulation of endothelial calcium signaling.

I is a cation current permeating the ISOC channel. In pulmonary endothelial cells, I activation leads to formation of inter-endothelial cell gaps and barrier disruption. The immunophilin FK506-binding protein 51 (FKBP51), in conjunction with the serine/threonine protein phosphatase 5C (PPP5C), inhibits I .

The Antitumor Drug LB-100 Is a Catalytic Inhibitor of Protein Phosphatase 2A (PPP2CA) and 5 (PPP5C) Coordinating with the Active-Site Catalytic Metals in PPP5C.

LB-100 is an experimental cancer therapeutic with cytotoxic activity against cancer cells in culture and antitumor activity in animals. The first phase I trial (NCT01837667) evaluating LB-100 recently concluded that safety and efficacy parameters are favorable for further clinical testing. Although LB-100 is widely reported as a specific inhibitor of serine/threonine phosphatase 2A (PP2AC/), we could find no experimental evidence in the published literature demonstrating the specific engagement of LB-100 with PP2A , in cultured cells, or in animals.

Serine/threonine phosphatase 5 (PP5C/PPP5C) regulates the ISOC channel through a PP5C-FKBP51 axis.

Pulmonary endothelial cells express a store-operated calcium entry current ( I), which contributes to inter-endothelial cell gap formation. I is regulated by a heterocomplex of proteins that includes the immunophilin FKBP51. FKBP51 inhibits I by mechanisms that are not fully understood.