MEGALIN-MEDIATED ENDOCYTOSIS IN RENAL PROXIMAL TUBULE

Megalin a 600 kDa membrane protein belonging to the IDL receptor famil y is highly expressed in the endocytic pathway of renal proximal tubul es. In addition, this receptor is found in several other epithelia fac ing transcellular fluids but is also expressed in the parathyroid glan ds. Recent studies have established this protein as probably the most important receptor for endocytosis of macromolecules filtered in the r enal glomeruli. The ligands reported to bind to megalin consist of a v ariety of different substances including albumin, vitamin-carrier comp lexes, proteinases and proteinase-inhibitor complexes, lipoprotein par ticles, receptor associated protein (RAP), different drugs and calcium .