Requirement of a dynein light chain in TGFbeta/Smad3 signaling

J Cell Physiol. 2009 Dec;221(3):707-15. doi: 10.1002/jcp.21910.

Abstract

We have previously reported that the dynein light chain (DLC) km23-1 is required for Smad2-dependent TGFbeta signaling. Here we describe another member of the km23/DYNLRB/LC7/robl family of DLCs, termed km23-2, which is also involved in TGFbeta signaling. We show not only that TGFbeta stimulates the interaction of km23-2 (DYNLRB2) with TGFbeta receptor II (TbetaRII) but also that TGFbeta regulates the interaction between km23-2 and endogenous TbetaRII in vivo. In addition, TGFbeta treatment causes km23-2 phosphorylation, whereas a kinase-deficient form of TbetaRII prevents km23-2 phosphorylation. In contrast to the km23-1 isoform, blockade of km23-2 expression using small interfering RNAs (siRNAs) decreased key TGFbeta/Smad3-specific responses, including the induction of both plasminogen activator inhibitor-1 (PAI-1) gene expression and p21 protein expression. Blockade of km23-1 expression had no effect on these two major TGFbeta/Smad3 responses under similar conditions. Further, km23-2 was required for TGFbeta stimulation of Smad3-dependent Smad-binding element (SBE)2-Luc transcriptional activity, but not for TGFbeta stimulation of Smad2-dependent activin responsive element (ARE)-Lux transcriptional activity. In order to assess the mechanisms underlying the preferential stimulation of Smad3- versus Smad2-specific TGFbeta responses, immunoprecipitation (IP)/blot analyses were performed, which demonstrate that TGFbeta stimulated preferential complex formation of km23-2 with Smad3, relative to Smad2. Collectively, our findings indicate that km23-2 is required for Smad3-dependent TGFbeta signaling. More importantly, we demonstrate that km23-2 has functions in TGFbeta signaling that are distinct from those for km23-1. This is the first report to describe a differential requirement for unique isoforms of a specific DLC family in Smad-specific TGFbeta signaling.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Cell Line
  • Cyclin-Dependent Kinase Inhibitor p21 / genetics
  • Cyclin-Dependent Kinase Inhibitor p21 / metabolism
  • Cytoplasmic Dyneins
  • Dyneins / genetics
  • Dyneins / metabolism
  • Dyneins / physiology*
  • Gene Expression / genetics
  • Humans
  • Mink
  • Neoplasm Proteins / physiology*
  • Phosphorylation / drug effects
  • Plasminogen Activator Inhibitor 1 / genetics
  • Plasminogen Activator Inhibitor 1 / metabolism
  • Protein Binding / drug effects
  • Protein Binding / physiology
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism
  • RNA, Small Interfering / genetics
  • Receptor, Transforming Growth Factor-beta Type I
  • Receptor, Transforming Growth Factor-beta Type II
  • Receptors, Transforming Growth Factor beta / genetics
  • Receptors, Transforming Growth Factor beta / metabolism
  • Signal Transduction / physiology*
  • Smad2 Protein / genetics
  • Smad2 Protein / metabolism
  • Smad3 Protein / genetics
  • Smad3 Protein / metabolism*
  • Transfection
  • Transforming Growth Factor beta / pharmacology
  • Transforming Growth Factor beta / physiology*

Substances

  • CDKN1A protein, human
  • Cyclin-Dependent Kinase Inhibitor p21
  • DYNLRB1 protein, human
  • Neoplasm Proteins
  • Plasminogen Activator Inhibitor 1
  • Protein Isoforms
  • RNA, Small Interfering
  • Receptors, Transforming Growth Factor beta
  • SERPINE1 protein, human
  • SMAD2 protein, human
  • SMAD3 protein, human
  • Smad2 Protein
  • Smad3 Protein
  • Transforming Growth Factor beta
  • Protein-Serine-Threonine Kinases
  • Receptor, Transforming Growth Factor-beta Type I
  • Receptor, Transforming Growth Factor-beta Type II
  • Cytoplasmic Dyneins
  • DYNLRB2 protein, human
  • Dyneins