This family consists of several mammalian CD34 antigen proteins. The CD34 antigen is a human leukocyte membrane protein expressed specifically by lymphohematopoietic progenitor cells. CD34 is a phosphoprotein. Activation of protein kinase C (PKC) has been found to enhance CD34 phosphorylation [1]. This family contains several eukaryotic podocalyxin proteins. Podocalyxin is a major membrane protein of the glomerular epithelium and is thought to be involved in maintenance of the architecture of the foot processes and filtration slits characteristic of this unique epithelium by virtue of its high negative charge. Podocalyxin functions as an anti-adhesin that maintains an open filtration pathway between neighbouring foot processes in the glomerular epithelium by charge repulsion [2].

1: Activated protein kinase C directly phosphorylates the CD34 antigen on hematopoietic cells. Fackler MJ, Civin CI, Sutherland DR, Baker MA, May WS; J Biol Chem 1990;265:11056-11061. PMID:1694174

2: Expression of podocalyxin inhibits cell-cell adhesion and modifies junctional properties in Madin-Darby canine kidney cells. Takeda T, Go WY, Orlando RA, Farquhar MG; Mol Biol Cell 2000;11:3219-3232. PMID:10982412

3: Identification of endoglycan, a member of the CD34/podocalyxin family of sialomucins. Sassetti C, Van Zante A, Rosen SD; J Biol Chem 2000;275:9001-9010. PMID:10722749