Proteins associated with migratory preparation-
Unlike the neuroendocrine system that regulates reproduction, no
specific neural center has yet been localized that controls the
migratory process. Migratory preparedness is characterized by increased
food intake, fat deposition, and locomotion (nighttime restlessness in
captivity; aka Zugunruhe , Trivedi et al., 2014; Singh et al.,
2015). We found several DEPs that have been studied in the control of
food intake and energy balance. Among the most relevant proteins that
were more abundant in migrants than residents were monocarboxylate
transport protein (MCT2) and apoptosis-inducing factor (AIF). MCT2 is
involved in the transport of short-chain monocarboxylates such as
pyruvate, ketone bodies, lactate and a-hydroxybutyrate, which play an
essential role in energy balance (Elizondo-Vegal, Salgado, &
Gracía-Robles, 2016). Studies of MCT2 protein in the regulation of food
intake have located it in both orexigenic and anorexigenic neurons
(Cortés-Campos et al. 2013). Specifically, projections from tanycyte
specialized ependymal cells found on the lining of third ventricle of
the brain communicate directly with MCT2 positive neurons that
synthesize and release key neuropeptides such as proopiomelanocortin
(POMC), agouti related protein (AgRP), and neuropeptide Y (NPY) that
control food intake (Elizondo-Vega et al., 2015). Similarly, AIF protein
is known for facilitating utilization of fatty acids for mitochondrial
respiration specific to hypothalamic POMC neurons involved in regulation
of glucose sensing and energy metabolism (Timper et al., 2018).
Locomotion and navigation are two other important behavioral features
that differentiate the migratory junco population from the earlier
reproducing resident population. During enhanced locomotor activity, one
would expect sustained stimulation of nerve synapses, synaptogenesis,
synaptic plasticity, and dendritic spine morphogenesis. We found greater
abundance of Stonin 2, NCK2, Septin 7, Dock 7 in migratory juncos, all
proteins that have been studied in relation to increased synaptogenesis,
synaptic plasticity, dendritic spine morphogenesis, and neurogenesis
(Jung et al., 2007; Thévenot et al., 2011; Wang et al., 2018). In
addition to proteins that are involved in neuronal plasticity, we also
found a member of a high mobility protein family (HMGN5) known to
regulate gene expression by modulating chromatin structure (Rochman,
Malicet, & Bustin, 2010). Other proteins present in high abundance in
migratory juncos were RSG7 regulators for G protein signaling (RGS) in
paraventricular neurons (PVN) (Gold, Ni, Dohlman, & Nestler et al.,
1997), LYRIC known to regulate inflammation, immune response, and
angiogenesis (Emdad et al., 2013), and SIK3 known to be associated with
regulation of corticotropin releasing hormone transcription in rat
hypothalamic neurons (Liu et al., 2012).