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Results for “seconds of phosphorylation events”

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PubMed2026

Deciphering the Protein Phosphorylation Dynamics Triggered by Seconds of Force Stimulation.

Plants perceive mechanical forces through phosphosignaling networks, but their relationship with gravity signaling remains elusive. To dissect gravity force signaling components, we performed SILIA-based phosphoproteomics on Arabidopsis aerial organs subjected to 20-s inversion or 30-s gravistimulation, identifying 2,733 and 2,878 phosphoproteins, respectively. Quantitative analysis revealed 34 significantly regulated phosphoproteins specific to inversion and 52 specific to gravistimulation. Inversion-specific phosphoproteins, associated with the initial calcium code, likely mediate calcium signals through EF-hand proteins, CPK1, and calmodulin-interacting proteins, potentially intersecting with receptor-like kinase-initiated MAPK cascades via RAF15 and MKK1/2 to induce gravitropic responses. Gravistimulation-specific phosphoproteins, linked to the secondary calcium code, function in calcium signaling/homeostasis (ACA8, ZAC, IQD2, ANNAT1), membrane vesicle trafficking (ABCG36, ARF-GAP8), and lipid signaling (PIP5K8/9), supporting auxin transport and stress signal transduction. Immunoblot validation confirmed treatment-associated phosphosites pS108-PATL3 and pS107-TREPH2, along with inversion-specific pS1145-ATEH2, exhibiting stem-specific phosphorylation enhancement and force-discriminatory responses. Functional analysis identified the integrin-like protein GREPH1 as a key gravitropism regulator, with greph1 mutants displaying reduced inflorescence stem gravicurvature. Notably, hyperphosphorylation of pS107-TREPH2 and pS1145-ATEH2 peaked at 20 to 50 s in greph1 mutants but persisted from 20 s to 2 h in WT plants. These findings establish a stem-enriched phosphorylation code for gravity force discrimination, with GREPH1 modulating spatiotemporal phosphoprotein dynamics and shoot gravicurvature, potentially functioning as a receptor reminiscent of sedimenting plastids.

Arabidopsis↗

PubMed1979

LH-induced desensitization of the adenylyl cyclase system in ovarian follicles.

Studies on the gonadotrophin-responsive adenylyl cyclase (AC) system of rabbit and porcine ovarian follicles reveal that hCG or LH-induced desensitization of the AC system can be divided into two phases: an initial, LH-specific phase and a second phase which is not specific for LH. The first phase occurs within the first hour after LH-hCG-receptor interaction, is agonist specific, and is not mediated by protein synthetic events or by cAMP. In view of our previous demonstration of the critical dependence of the LH-induced desensitizing process in cell-free membrane preparations of porcine follicles upon Mg2+ and ATP, we investigated the role of a phosphorylation reaction in the first phase of the AC desensitizing process. Porcine follicular membranes rich in LH-sensitive AC activity were found to contain the molecular requirements necessary for a phosphorylation reaction: namely, cAMP-dependent and cAMP-independent protein kinases as well as phosphoprotein phosphatases. The following lines of indirect evidence indicated that reversal or resensitization of the desenzitized AC system to LH was mediated by a dephosphorylation reaction. Activators of endogenous phosphoprotein phosphatases--Mn2+ and dithiothreitol--promoted a specific resensitization of the follicular AC system to LH. Likewise, a partially purified phosphoprotein phosphatase also resensitized the desensitized, LH unresponsive AC to LH, and boiling of the phosphatase prevented its effect. LH-induced desensitization of the AC system, on the other hand, did not appear to be mediated by a cAMP-dependent protein kinase, as evidenced both by the inability of beef heart protein to promote desensitization of AC and by the inability of an inhibitor of cAMP-dependent protein kinase to prevent LH-induced densensitization. The second phase of desensitization, which occurs after the first hour following hCG-LH-receptor interaction, is characterized by a loss of responsiveness to FSH as well as to LH and can be promoted by dibutryl cAMP (in the absence of LH). These results provide new evidence on the characteristics and molecular mechanism of LH-induced densensitization of the follicular AC system. These results indicate that the level of phosphorylation of membrane-associated components may, in part, regulate the activity of the AC system during this first phase of homologous desensitization.

Adenylyl Cyclases↗

PubMed1979

The src gene product of transformed and morphologically reverted ASV-infected mammalian cells.

Morphological revertants of avian sarcoma virus transformed vole cells contain the sarcoma gene product (pp60src) in an enzymatically active form, suggesting that the presence of pp60src protein kinase activity is infussicient to induce morphological transformation. Structural analyses of pp60src from infected vole cell clones suggest that in one of the revertant clones on alteration in pp60src may be responsible for morphological reversion while in a second clone, reversion may result from an alteration in a cell gene product with which pp60src must interact. As these morphological revertant cells are tumorigenic, different cell components are required to interact with pp60src to facilitate the two events.

Animals↗

PubMed1978

The "second messenger" system in brown adipose tissue of developing rats. Its molecular composition and mechanism of function.

Our studies of the hormonal receptor system and of the sequence of enzymatic events interconnecting the initial hormonal stimulus to the brown adipocyte with its final subcellular effect are summarized here. The hormone-mediated regulatory pathway consists of the adenyl cyclase and the protein kinase systems; the former is composed of the receptor and catalytic sites, the latter of regulatory and catalytic subunits. Emphasis is given currently to the diversity and characteristics of the individual components of the protein kinase system, since it seems to carry out the ultimate unifying mechanism involved in a variety of hormone-mediated functions, i.e. the phosphorylation of a protein molecule.

Adenylyl Cyclases↗

PubMed1978

Simulation of coupling between chemical reactions and ion transport in brown adipose tissue using network thermodynamics.

Several cellular events associated with energy turnover in the mitochondria and at the Na+/K+ plasma membrane pump have been formulated in terms of network thermodynamics. The calorigenic role of the Na+/K+ pump is examined in terms of the relationship between the movement of sodium and potassium ions and the chemical reactions involved. In addition, attention is centered on the potential thermogenic role of three mitochondrial pathways involving proton fluxes--namely, one in which protons are transported from the matrix to the intermembrane space; a second in which protons are transferred back into the matrix in conjunction with the synthesis of ATP; and a third wherein protons re-enter the matrix without being coupled to any chemical reaction. (This latter pathway has been delineated by studies on isolated mitochondria and may be unique to brown fat.) At both sites (plasma membrane and mitochondria) the conversion of chemical energy to heat is considered.

Adenosine Triphosphate↗