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Synaptopodin: an actin-associated protein in telencephalic dendrites and renal podocytes.

Mundel P, Heid HW, Mundel TM, Krüger M, Reiser J, Kriz W - J. Cell Biol. (1997)

Bottom Line: In particular, synaptopodin does not contain functional domains found in receptor-clustering PSD proteins.The exclusive synaptopodin synthesis in the telencephalon has been confirmed by in situ hybridization, where synaptopodin mRNA is only found in perikarya of the olfactory bulb, cerebral cortex, striatum, and hippocampus, i.e., the expression is restricted to areas of high synaptic plasticity.From these results and experiments with cultured cells we conclude that synaptopodin represents a novel kind of proline-rich, actin-associated protein that may play a role in modulating actin-based shape and motility of dendritic spines and podocyte foot processes.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, University of Heidelberg, Germany. peter.mundel@urz.uni-heidelberg.de

ABSTRACT
Synaptopodin is an actin-associated protein of differentiated podocytes that also occurs as part of the actin cytoskeleton of postsynaptic densities (PSD) and associated dendritic spines in a subpopulation of exclusively telencephalic synapses. Amino acid sequences determined in purified rat kidney and forebrain synaptopodin and derived from human and mouse brain cDNA clones show no significant homology to any known protein. In particular, synaptopodin does not contain functional domains found in receptor-clustering PSD proteins. The open reading frame of synaptopodin encodes a polypeptide with a calculated Mr of 73.7 kD (human)/74.0 kD (mouse) and an isoelectric point of 9.38 (human)/9. 27 (mouse). Synaptopodin contains a high amount of proline ( approximately 20%) equally distributed along the protein, thus virtually excluding the formation of any globular domain. Sequence comparison between human and mouse synaptopodin revealed 84% identity at the protein level. In both brain and kidney, in vivo and in vitro, synaptopodin gene expression is differentiation dependent. During postnatal maturation of rat brain, synaptopodin is first detected by Western blot analysis at day 15 and reaches maximum expression in the adult animal. The exclusive synaptopodin synthesis in the telencephalon has been confirmed by in situ hybridization, where synaptopodin mRNA is only found in perikarya of the olfactory bulb, cerebral cortex, striatum, and hippocampus, i.e., the expression is restricted to areas of high synaptic plasticity. From these results and experiments with cultured cells we conclude that synaptopodin represents a novel kind of proline-rich, actin-associated protein that may play a role in modulating actin-based shape and motility of dendritic spines and podocyte foot processes.

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Maturation-dependent expression of synaptopodin during postnatal development of rat brain. (a)  Cytosolic extracts from cerebellum and forebrain harvested at day 5, 10, 15, and 20  postnatal and from adult rats  were analyzed by Western  blotting. In the cerebellum,  synaptopodin was never expressed. In the forebrain,  synaptopodin first appeared  around day 15, increased  thereafter, and reached the  maximum level of expression  in the adult animal. (b) The  identical membrane was probed with anti-tubulin to prove equal  protein loading in all lanes.
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Figure 9: Maturation-dependent expression of synaptopodin during postnatal development of rat brain. (a) Cytosolic extracts from cerebellum and forebrain harvested at day 5, 10, 15, and 20 postnatal and from adult rats were analyzed by Western blotting. In the cerebellum, synaptopodin was never expressed. In the forebrain, synaptopodin first appeared around day 15, increased thereafter, and reached the maximum level of expression in the adult animal. (b) The identical membrane was probed with anti-tubulin to prove equal protein loading in all lanes.

Mentions: To examine the maturation-dependent expression of synaptopodin during brain development, we analyzed cytosolic extract from rat forebrains and cerebella at postnatal days 5, 10, 15, 20, and 50 by Western blotting. Synaptopodin was first expressed around day 15, increased thereafter, and reached the maximum level of expression in the adult brain (Fig. 9). Like in the adult brain, no expression of synaptopodin was observed in the cerebellum during postnatal maturation. To prove equal protein loading, blot membranes were probed with anti-tubulin antibody and showed comparable signal intensity in all lanes (data not shown).


Synaptopodin: an actin-associated protein in telencephalic dendrites and renal podocytes.

Mundel P, Heid HW, Mundel TM, Krüger M, Reiser J, Kriz W - J. Cell Biol. (1997)

Maturation-dependent expression of synaptopodin during postnatal development of rat brain. (a)  Cytosolic extracts from cerebellum and forebrain harvested at day 5, 10, 15, and 20  postnatal and from adult rats  were analyzed by Western  blotting. In the cerebellum,  synaptopodin was never expressed. In the forebrain,  synaptopodin first appeared  around day 15, increased  thereafter, and reached the  maximum level of expression  in the adult animal. (b) The  identical membrane was probed with anti-tubulin to prove equal  protein loading in all lanes.
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Related In: Results  -  Collection

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Figure 9: Maturation-dependent expression of synaptopodin during postnatal development of rat brain. (a) Cytosolic extracts from cerebellum and forebrain harvested at day 5, 10, 15, and 20 postnatal and from adult rats were analyzed by Western blotting. In the cerebellum, synaptopodin was never expressed. In the forebrain, synaptopodin first appeared around day 15, increased thereafter, and reached the maximum level of expression in the adult animal. (b) The identical membrane was probed with anti-tubulin to prove equal protein loading in all lanes.
Mentions: To examine the maturation-dependent expression of synaptopodin during brain development, we analyzed cytosolic extract from rat forebrains and cerebella at postnatal days 5, 10, 15, 20, and 50 by Western blotting. Synaptopodin was first expressed around day 15, increased thereafter, and reached the maximum level of expression in the adult brain (Fig. 9). Like in the adult brain, no expression of synaptopodin was observed in the cerebellum during postnatal maturation. To prove equal protein loading, blot membranes were probed with anti-tubulin antibody and showed comparable signal intensity in all lanes (data not shown).

Bottom Line: In particular, synaptopodin does not contain functional domains found in receptor-clustering PSD proteins.The exclusive synaptopodin synthesis in the telencephalon has been confirmed by in situ hybridization, where synaptopodin mRNA is only found in perikarya of the olfactory bulb, cerebral cortex, striatum, and hippocampus, i.e., the expression is restricted to areas of high synaptic plasticity.From these results and experiments with cultured cells we conclude that synaptopodin represents a novel kind of proline-rich, actin-associated protein that may play a role in modulating actin-based shape and motility of dendritic spines and podocyte foot processes.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, University of Heidelberg, Germany. peter.mundel@urz.uni-heidelberg.de

ABSTRACT
Synaptopodin is an actin-associated protein of differentiated podocytes that also occurs as part of the actin cytoskeleton of postsynaptic densities (PSD) and associated dendritic spines in a subpopulation of exclusively telencephalic synapses. Amino acid sequences determined in purified rat kidney and forebrain synaptopodin and derived from human and mouse brain cDNA clones show no significant homology to any known protein. In particular, synaptopodin does not contain functional domains found in receptor-clustering PSD proteins. The open reading frame of synaptopodin encodes a polypeptide with a calculated Mr of 73.7 kD (human)/74.0 kD (mouse) and an isoelectric point of 9.38 (human)/9. 27 (mouse). Synaptopodin contains a high amount of proline ( approximately 20%) equally distributed along the protein, thus virtually excluding the formation of any globular domain. Sequence comparison between human and mouse synaptopodin revealed 84% identity at the protein level. In both brain and kidney, in vivo and in vitro, synaptopodin gene expression is differentiation dependent. During postnatal maturation of rat brain, synaptopodin is first detected by Western blot analysis at day 15 and reaches maximum expression in the adult animal. The exclusive synaptopodin synthesis in the telencephalon has been confirmed by in situ hybridization, where synaptopodin mRNA is only found in perikarya of the olfactory bulb, cerebral cortex, striatum, and hippocampus, i.e., the expression is restricted to areas of high synaptic plasticity. From these results and experiments with cultured cells we conclude that synaptopodin represents a novel kind of proline-rich, actin-associated protein that may play a role in modulating actin-based shape and motility of dendritic spines and podocyte foot processes.

Show MeSH