Spectrin alpha is important for rear polarization of the microtubule organizing center during migration and spindle pole assembly during division of neointimal smooth muscle cells

Abstract

Directed migration of smooth muscle cells (SMCs) from the media to the intima and their subsequent proliferation are key events in atherosclerosis as these cells contribute to the bulk and stability of atheromatous plaques. We showed previously that two cytoskeleton-associated proteins, RHAMM and ARPC5, play important roles in rear polarization of the microtubule organizing centre (MTOC), directed migration, and in maintaining cell division fidelity. These proteins were analyzed to predict additional potential interacting partners using the bioinformatics programs BLAST, ClustalW, and PPI Spider. We identified spectrin alpha, a protein with a known role in actin polymerization as part of the pathway. We show that in migrating SMCs spectrin alpha localizes at the nodes of the actin net, and it partially colocalizes with RHAMM in the perinuclear region. In dividing SMCs spectrin alpha is present at spindle poles and midbody. Moreover, we show that spectrin alpha and RHAMM interact in a complex. Using siRNA to knockdown spectrin disrupted SMC migration, MTOC polarization, and the assembly of a polygonal actin net dorsolateral of the nucleus. Spectrin alpha knockdown also disrupted the organization of the bipolar spindle, chromosome division, and cytokinesis during cell division. The identification of interacting partners such as spectrin alpha and the decoding of pathways involved in polarity regulation during the migration of smooth muscle cells in atherosclerosis is important for identifying atherosclerosis biomarkers and developing therapeutic agents to block atherosclerotic plaque formation.

The roles and regulation of the actin cytoskeleton, intermediate filaments and microtubules in smooth muscle cell migration

“…Spectrin-α (an actin-associated protein) colocalizes with RHAMM at the nodes of the actin net. Thus, spectrin-α interacts with RHAMM to regulate microtubule polarization in smooth muscle cells [82]. …”

Carcinoma Cell Hyaluronan as a “Portable” Cancerized Prometastatic Microenvironment

“…Subsequent studies demonstrated that RHAMM also has diverse and complex subcellular functions. The binding partners of intracellular RHAMM vary with cell and tissue background but include kinases/activators such as ERK1, 2/MEK1 [4] SRC [3] and AURKA/TPX2 [38] as well as nuclear proteins, microtubule and actin binding proteins such as spectrin alpha [50] and supervillin [51]. The functional association of intracellular RHAMM with AURKA/TPX2 is linked to breast cancer risk in BRCA1, 2 carriers predicting key functional roles for these intracellular RHAMM complexes in tumor susceptibility and aggression [38].…”

Nuclear alpha spectrin: Critical roles in DNA interstrand cross-link repair and genomic stability

“…aIISp in cell cycle progression a-spectrin is also important for cell cycle progression where it is required for proper cytokinesis and coordination of events involved in cell division such as organization of the spindle pole and cytokinesis. 101 It plays a key role in linking the actin cytoskeleton to various cell components, such as microtubules, needed in cell division. [101][102][103] A deficiency in a-spectrin in cells could significantly affect progression of the cell cycle.…”

“…101 It plays a key role in linking the actin cytoskeleton to various cell components, such as microtubules, needed in cell division. [101][102][103] A deficiency in a-spectrin in cells could significantly affect progression of the cell cycle.…”