Alternative Splice Variants of Doublecortin-like Kinase Are Differentially Expressed and Have Different Kinase Activities

Abstract

Alternative splicing of mRNA transcripts expands the range of protein products from a single gene locus. Several splice variants of DCLK (doublecortin-like kinase) have previously been reported. Here, we report the genomic organization underlying the splice variants of DCLK and examine the expression profile of two splice variants affecting the kinase domain of DCLK and CPG16 (candidate plasticity gene 16), one containing an Arg-rich domain and the other affecting the C terminus of the protein. These splice alternatives were differentially expressed in embryonic and adult brain. Both splice variants disrupted DCLK PEST domains; however, all splice variants remained sensitive to proteolysis by calpain. The adult-specific C-terminal splice variant of DCLK had reduced autophosphorylation activity, but similar kinase activity for myelin basic protein relative to the embryonic splice variant. The splice variant adding an Arg-rich domain gained an autophosphorylation site at Ser-382. Although this protein isoform was expressed mainly in the adult brain, the phosphorylated form was strongly enriched in embryonic brain and adult olfactory bulb, suggesting a possible role in migrating neurons.The majority of neuronal cells in the central nervous system are generated during embryogenesis and persist throughout life without further rounds of division and differentiation. Individual neurons accomplish an array of distinct tasks during their life span, including cellular migration, axon extension and pathfinding, synaptogenesis, and participation in mature nervous system function. It has been suggested that to deal with these diverse demands on cellular function, the repertoire of neuronal gene products is enhanced by alternative splicing and RNA editing. Following the description of differential RNA processing of the calcitonin gene (1), alternative splice forms of many gene products have been detected in the central nervous system (2, 3). Doublecortin-like kinase (DCLK) 1 is a serine-threonine kinase expressed in the central nervous system. The N-terminal domain of DCLK is very similar to the doublecortin protein and mediates microtubule localization (4 -6). The C-terminal kinase domain of DCLK resembles members of the family of calcium/calmodulin-dependent protein kinases, but lacks a canonical calmodulin-binding site (7). The human gene was named DCAMKL1 (doublecortin-and Ca 2ϩ /calmodulindependent protein kinase-like protein-1) (8); however, biochemical evidence does not indicate that calcium/calmodulin modulates kinase activity (7).The DCLK locus gives rise to several transcripts through differential splicing and use of alternative promoters (see Fig. 1). The DCL product includes the doublecortin domain, but lacks the kinase domain. DCLK Rϩ is a full-length transcript embracing both doublecortin and kinase domains and includes an additional 16 amino acids enriched in arginine residues (the Arg-rich domain), between the doublecortin and kinase domains (9). Two splice variants affecting the final coding exon of DCLK hav...

Both Doublecortin and Doublecortin-Like Kinase Play a Role in Cortical Interneuron Migration

“…The two genes show overlapping expression patterns, although DCLK is more widely expressed in the brain (Sossey-Alaoui and Srivastava, 1999;Burgess and Reiner, 2000). In addition, DCLK encodes multiple transcripts, which are all differently regulated and may have different functions (Hevroni et al, 1998;Burgess et al, 1999;Silverman et al, 1999;Vreugdenhil et al, 2001;Burgess and Reiner, 2002). Two groups have recently reported that, although Dcx or Dclk mutant mice do not show defects in radial neuronal migration, mutants for both Dcx and Dclk genes display cortical lamination defects, suggesting that they can functionally compensate each other (Deuel et al, 2006;Koizumi et al, 2006a).…”

The DCX Superfamily 1: Common and Divergent Roles for Members of the Mouse DCX Superfamily

“…3C). An additional protein examined, DCL (a normal product of the DCLK gene lacking the kinase domain) 30 allowed the formation of MT that exhibited high stability to the cold (Fig. 3D).…”

Region-specific transcriptional changes following the three antidepressant treatments electro convulsive therapy, sleep deprivation and fluoxetine

“…71 The activity and neurotransmitter-induced early gene protein 4 (Ania-4) shares high homology with doublecortin-like kinase, CaM-Kinase, the CaMKrelated peptide (CARP) and the candidate plasticity gene 16 (CPG16), a protein serine/threonine kinase. 72,73 Ania-4, together with Homer and Erg2, is upregulated in the striatum by dopaminergic stimulation. 74 Ania-4 expression is also elevated in the cerebral cortex after traumatic brain injury and in the striatum following treatment with the putative D1 agonist/D2 antagonist LEK8829.…”