Immunoreactivity to Neurofilaments in the Rodent Anterior Pituitary is Associated with the Expression of α1A Protein Subunits of Voltage-Gated Ca2+ Channels

Immunoreactivity to Neurofilaments in the Rodent Anterior Pituitary is Associated with the Expression of α1A Protein Subunits of Voltage-Gated Ca2+ Channels. Fiordelisio, T., Jiménez, N., Baba, S., Shiba, K., & Hernández-Cruz, A. Journal of Neuroendocrinology, 19(11):870–881, 2007. _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2826.2007.01596.x

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We recently reported that rodent anterior pituitary (AP) cells (with the exception of corticotrophs and melanotrophs) express neuronal markers, including 68-kDa neurofilaments (NF68) in an oestrogen-dependent manner. The functional significance of neurofilament (NF) expression in the AP is unknown, but recent data in myelinated nerve fibres from NF-null mice suggest that NFs can regulate ion channel function. Because Ca2+ influx through voltage-gated Ca2+ channels is required for hormone secretion in AP cells, and oestrogen regulates the expression of Ca2+ channels in AP cells, the present study examined the expression of α1 subunits of voltage gated Ca2+ channels in relation to that of NF68. Using quantitative immunofluorescence, we demonstrate that α1C and α1D subunits are abundantly expressed in female AP cells, α1A subunits are moderately expressed, and α1G and α1B subunits are expressed at the lowest levels. Double-immunostaining showed that NF68 expression is not correlated with that of α1C, α1D or α1B. Expression of α1G and NF68 appear to be mutually exclusive from each other. Moreover, α1A subunit and NF68 expression are significantly correlated and α1A immunoreactivity is sexually dimorphic (i.e. low in males and high in females) and its levels of expression vary during the oestrous cycle, similar to NF68. Finally, ω-agatoxin IVA, a specific blocker of P/Q type Ca2+ currents that are a result of the activity of α1A subunits, inhibited to a greater extent spontaneous [Ca2+]i fluctuations in AP cells from females in oestrous and dioestrous, whereas cells from females in pro-oestrous and males were less affected by this toxin. These results suggest a preferential participation of P/Q-type Ca2+ channels and hence α1A subunits, in regulating spontaneous Ca2+ transients in AP cells under conditions where the proportion of NF68-expressing cells is high. It remains to be determined whether the expression of NF68 affects that of α1A Ca2+ channel subunits or vice versa.

@article{fiordelisio_immunoreactivity_2007,
	title = {Immunoreactivity to {Neurofilaments} in the {Rodent} {Anterior} {Pituitary} is {Associated} with the {Expression} of α{1A} {Protein} {Subunits} of {Voltage}-{Gated} {Ca2}+ {Channels}},
	volume = {19},
	issn = {1365-2826},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2826.2007.01596.x},
	doi = {10.1111/j.1365-2826.2007.01596.x},
	abstract = {We recently reported that rodent anterior pituitary (AP) cells (with the exception of corticotrophs and melanotrophs) express neuronal markers, including 68-kDa neurofilaments (NF68) in an oestrogen-dependent manner. The functional significance of neurofilament (NF) expression in the AP is unknown, but recent data in myelinated nerve fibres from NF-null mice suggest that NFs can regulate ion channel function. Because Ca2+ influx through voltage-gated Ca2+ channels is required for hormone secretion in AP cells, and oestrogen regulates the expression of Ca2+ channels in AP cells, the present study examined the expression of α1 subunits of voltage gated Ca2+ channels in relation to that of NF68. Using quantitative immunofluorescence, we demonstrate that α1C and α1D subunits are abundantly expressed in female AP cells, α1A subunits are moderately expressed, and α1G and α1B subunits are expressed at the lowest levels. Double-immunostaining showed that NF68 expression is not correlated with that of α1C, α1D or α1B. Expression of α1G and NF68 appear to be mutually exclusive from each other. Moreover, α1A subunit and NF68 expression are significantly correlated and α1A immunoreactivity is sexually dimorphic (i.e. low in males and high in females) and its levels of expression vary during the oestrous cycle, similar to NF68. Finally, ω-agatoxin IVA, a specific blocker of P/Q type Ca2+ currents that are a result of the activity of α1A subunits, inhibited to a greater extent spontaneous [Ca2+]i fluctuations in AP cells from females in oestrous and dioestrous, whereas cells from females in pro-oestrous and males were less affected by this toxin. These results suggest a preferential participation of P/Q-type Ca2+ channels and hence α1A subunits, in regulating spontaneous Ca2+ transients in AP cells under conditions where the proportion of NF68-expressing cells is high. It remains to be determined whether the expression of NF68 affects that of α1A Ca2+ channel subunits or vice versa.},
	language = {en},
	number = {11},
	urldate = {2021-07-27},
	journal = {Journal of Neuroendocrinology},
	author = {Fiordelisio, T. and Jiménez, N. and Baba, S. and Shiba, K. and Hernández-Cruz, A.},
	year = {2007},
	note = {\_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2826.2007.01596.x},
	keywords = {anterior pituitary subpopulations, neurofilament, oestrogen, pituitary, voltage-gated Ca2+ channels},
	pages = {870--881},
}

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