Acidic calponin immunoreactivity in postnatal rat brain and cultures: subcellular localization in growth cones, under the plasma membrane and along actin and glial filaments

Abstract

Acidic calponin, an F-actin-binding protein, is particularly enriched in brain, where calponin protein and mRNA are mainly expressed by neurons. The presence of calponin immunoreactivity in cultured astroglial cells has been reported, but the presence of acidic calponin in astrocytes in vivo appears equivocal. For the present study, we raised a specific polyclonal antibody against the 16-residue synthetic peptide covering the sequence E311-Q326 (EYPDEYPREYQYGDDQ) situated at the carboxy-terminal end of rat acidic calponin, and we investigated the cellular and subcellular localization of the protein in the developing central nervous system. Our results show that acidic calponin is particularly enriched in: (i) growth cones and submembranous fields of maturing cerebellar and cortical cells, where it codistributes with microfilaments and (ii) glial cells in vivo, including radial glia, glia limitans, Bergmann glia and mature astrocytes, and ex vivo, where acidic calponin strongly colocalizes with intermediate glial fibrillary acidic protein (GFAP) and vimentin filaments. Finally, up to four acidic calponin subtypes with different isoelectric point (pI) values were identified by two-dimensional gel electrophoresis of cerebellar and hippocampal extracts. The more acidic isoforms were developmentally regulated. As only one single mRNA for acidic calponin has been identified, these isoforms must reflect postsynthesis changes probably related to the particular functions of acidic calponin in maturing cells. Although brain acidic calponin's exact role remains uncertain, the present data suggest that it is involved in neuronal and glial plasticity.

Identification of Differentially Expressed Genes in Scrapie-Infected Mouse Brains by Using Global Gene Expression Technology

“…Both annexins and calponins were found to interact with cytoskeletal filaments such as F-actin. In addition, calponin was observed to colocalize with the two major intermediate filaments GFAP and vimentin in astrocytes (19,44). A recent work demonstrated that the blockage of expression of GFAP and vimentin in astrocytes supports axonal regeneration in the central nervous system of mammals (45), indicating a correlation between the intermediate filaments in astrocytes and the maintenance of neuronal cells.…”

“…The S100 proteins have been detected in both neurons and glial cells (18,52,55) and are thought to be involved in gliosis and neuronal apoptosis (16,52). S100 proteins have numerous targets, including annexins and calponins (44). Both annexins and calponins were found to interact with cytoskeletal filaments such as F-actin.…”

Expression of Calponin 3 in the Striatum Following 3-Nitropropionic Acid-induced Neurotoxicity

“…Although calponin 1 and 2 are predominantly expressed in smooth muscle cells, calponin 3 is highly expressed in the central nervous system and its expression level is increased in neuropathologic conditions such as epilepsy. In the central nervous system calponin 3 protein and its mRNA are mainly expressed in neurons under normal conditions [11]. Interestingly, calponin 3 is co-localized with PSD95, GluR1 and NR1 in the central nervous system and over-expression of calponin 3 in the cultured hippocampal neurons enhances the frequency of miniature ex-citatory postsynaptic currents.…”

“…On the other hand, calponin 3 is highly expressed in many tissues including articular cartilage and brain [6,11]. In the central nervous system, calponin 3 is co-localized with PSD95, NR1 and GluR1.…”

Enhancement of axonal regeneration by in vitro conditioning and its inhibition by cyclopentenone prostaglandins

“…Both glutathione-S-transferase and metallothionein have neuroprotective functions (Townsend and Tew, 2003;Penkowa et al, 2005). In cultured DRG, upregulation of other genes that might be important for axonal regeneration include vimentin, which is involved in retrograde axonal transport of activating signals for initiation of axonal growth (Hanz et al, 2003;Perlson et al, 2005), and the cytoskeletal proteins paxillin and calponin (Huang et al, 2004;Plantier et al, 1999). Vg1RBP is also of interest because, in developing neurons, it is involved in the translocation of mRNAs to growth cones Piper et al, 2006) but might also be important during axonal regeneration.…”