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Process formation of podocytes: morphogenetic activity of microtubules and regulation by protein serine/threonine

N Kobayashi1, J Reiser, K Schwarz

  • 1Department of Medicine and Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.

Histochemistry and Cell Biology
|May 1, 2001
PubMed

Insights

Microtubules (MTs), not actin filaments, are crucial for forming podocyte cell processes during development. The serine/threonine phosphatase PP2A regulates this process via dephosphorylation, offering insights into kidney diseases.

Area of Science:

  • Cell Biology
  • Developmental Biology
  • Nephrology

Background:

  • Podocytes are vital kidney cells with complex structures maintained by cytoskeletal elements like microtubules (MTs) and actin filaments (AFs).
  • The developmental regulation of podocyte process formation, crucial for kidney function, remains poorly understood.
  • Previous studies highlighted the importance of cytoskeletal elements but lacked insight into their developmental control.

Purpose of the Study:

  • To investigate the role of microtubules and actin filaments in the developmental regulation of podocyte process formation.
  • To identify the signaling pathways involved in podocyte cytoskeleton development.
  • To explore the potential involvement of protein phosphatases in regulating podocyte morphogenesis.

Main Methods:

  • Utilized a conditionally immortalized mouse podocyte cell line capable of in vivo-like process development.
  • Applied reagents to disrupt cytoskeletal elements (MTs, AFs) and inhibit protein phosphatases (PP2A).
  • Employed techniques including immunofluorescence microscopy and one- and two-dimensional Western blot analyses.

Main Results:

  • Microtubules (MTs) colocalized with vimentin intermediate filaments, while actin filaments (AFs) were distinct.
  • Depolymerization of MTs led to loss of podocyte processes and cell rounding, whereas AF disassembly had minimal impact.
  • Inhibition of MT elongation (vinblastine) or PP2A (okadaic acid) abolished process formation.
  • PP2A expression decreased during podocyte differentiation, and its inhibition increased serine/threonine phosphorylation.

Conclusions:

  • Microtubule morphogenetic activity is essential for podocyte process formation during development.
  • Podocyte process formation is regulated by serine/threonine protein dephosphorylation mediated by protein phosphatase 2A (PP2A).
  • These findings provide novel insights into the signaling mechanisms governing podocyte cytoskeleton development and potential implications for glomerular diseases.

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