Podocalyxin in human haematopoietic cells

Abstract

Summary Podocalyxin‐like protein (PCLP) is a sialomucin‐type membrane protein structurally related to CD34 and endoglycan. It was first described in glomerular podocytes and endothelial cells. In mice, PCLP is present in haemangioblasts, and in both chicken and mice it is a marker of early haematopoietic stem cells and lineage‐restricted haematopoietic progenitors. Its expression decreases during differentiation of haematopoietic cells. Of mature blood cells, only chicken and rat thrombocytes express PCLP protein. PCLP expression in human haematopoietic cells has not been studied. Here we demonstrate PCLP mRNA in human CD34+ cells, in lineage committed erythroid, megakaryocyte and myeloid progenitors, in K562 leukaemia cells, and in peripheral blood leucocytes. The mRNA expression level was higher in developing cells than in mature leucocytes. By Northern blotting and cDNA sequencing, the haematopoietic and renal PCLP mRNAs were identical. Of the mobilized CD34+ cells, 28% (mean; range 14–61%) expressed PCLP protein and the majority of PCLP+ cells were CD117+. Almost all of the K562 cells expressed PCLP protein. Surprisingly, PCLP protein was not detected in any mature blood cells. These results suggest that human PCLP may be a valuable marker for a subset of haematopoietic stem cells.

Magnetic Separation of Human Podocalyxin-like Protein 1 (hPCLP1)-Positive Cells from Peripheral Blood and Umbilical Cord Blood Using Anti-hPCLP1 Monoclonal Antibody and Protein A Expressed on Bacterial Magnetic Particles

“…Macrophage colonystimulating factor modulates the development of hematopoiesis by stimulating the differentiation of PCLP1 + CD45 -cells to endothelial cells in the AGM region. In humans, previous studies suggested that PCLP1 may be a useful marker for a subset of hematopoietic stem cells (Kerosuo et al, 2004). Here, we developed a monoclonal antibody against extracellular region of human PCLP1 (hPCLP1), termed 53D11.…”

“…2A). In addition, 53D11 was found to react to endogenous hPCLP1 expressed on MCF-7, a breast carcinoma cell line, which has been proved to express PCLP1 (Kerosuo et al, 2004;Somasiri et al, 2004) (Fig. 2B).…”

“…The expression of podocalyxin has been shown to block hematopoietic and epithelial cell adhesion and cell-cell contact (Takeda et al, 2000). In humans, PCLP1 expression decreases during hematopoietic cell maturation, and PCLP1 is likely a marker for a subset of these stem cells (Kerosuo et al, 2004). However, the function of PCLP1 in human hematopoietic cells has yet to be clearly understood because PCLP1 + cells are a minor component of mononuclear cells and therefore the isolation of these cells is difficult.…”

Control of cell adhesion and migration by podocalyxin. Implication of Rac1 and Cdc42

“…PODXL has also been found in vascular endothelium, lung, brain, multipotent hematopoietic precursors, megakaryocytes and platelets [4,14,15], as well as in several types of tumors in which the expression levels appear to correlate with the metastatic capacity [16,17,18]. However, unlike the role of PODXL in the renal homeostasis, almost nothing is known about its physiological role in extrarenal tissues.…”

Urinary biomarkers of diabetic nephropathy

“…Earlier studies used podocalyxin as the marker of choice in identifying podocytes, but their specificity was hampered because this protein is expressed also on endothelial cells, parietal epithelial cells, and a variety of nonrenal cells, such as platelets and hematopoietic stem cells. [74][75][76][77] Markers of the podocyte slit diaphragm, ie, nephrin and podocin, as well as the cytoskeletal protein synaptopodin, are known to be downregulated in diabetic nephropathy, 78 perhaps signifying shedding of these cells in the urine, rendering them a reasonable urinary marker. The sensitivity of podocyturia, as identified by nephrin for diagnosis, was demonstrated when urinary nephrin (nephrinuria) was found in a substantial number of normoalbuminuric patients, in addition to microalbuminuric and normoalbuminuric patients.…”